Shield
Overview
 
A shield is a type of personal armor
Personal armor
Personal armor is the whole of protecting clothing, designed to absorb and/or deflect slashing, bludgeoning, and penetrating attacks. They were historically used to protect soldiers, whereas today, they are also used to protect police forces, private citizens and private security guards or...

, meant to intercept attacks, either by stopping projectiles such as arrow
Arrow
An arrow is a shafted projectile that is shot with a bow. It predates recorded history and is common to most cultures.An arrow usually consists of a shaft with an arrowhead attached to the front end, with fletchings and a nock at the other.- History:...

s or redirecting a hit from a sword
Sword
A sword is a bladed weapon used primarily for cutting or thrusting. The precise definition of the term varies with the historical epoch or the geographical region under consideration...

, mace or battle axe
Battle axe
A battle axe is an axe specifically designed for combat. Battle axes were specialized versions of utility axes...

 to the side of the shield-bearer.

Shields vary greatly in size, ranging from large panels that protect the user's entire body to small models (such as the buckler
Buckler
A buckler is a small shield, 15 to 45 cm in diameter, gripped in the fist; it was generally used as a companion weapon in hand-to-hand combat during the Medieval and Renaissance, as its size made it poor protection against missile weapons but useful in deflecting the blow of...

) that were intended for hand-to-hand-combat use. Shields also vary a great deal in thickness; whereas some shields were made of relatively deep, absorbent, wooden planking to protect soldiers from the impact of spear
Spear
A spear is a pole weapon consisting of a shaft, usually of wood, with a pointed head.The head may be simply the sharpened end of the shaft itself, as is the case with bamboo spears, or it may be made of a more durable material fastened to the shaft, such as flint, obsidian, iron, steel or...

s and crossbow
Crossbow
A crossbow is a weapon consisting of a bow mounted on a stock that shoots projectiles, often called bolts or quarrels. The medieval crossbow was called by many names, most of which derived from the word ballista, a torsion engine resembling a crossbow in appearance.Historically, crossbows played a...

 bolts, others were thinner and lighter and designed mainly for deflecting blade strikes.

In prehistory and during the era of the earliest civilizations, shields were made of wood, animal hide, woven reeds or wicker.
Encyclopedia
A shield is a type of personal armor
Personal armor
Personal armor is the whole of protecting clothing, designed to absorb and/or deflect slashing, bludgeoning, and penetrating attacks. They were historically used to protect soldiers, whereas today, they are also used to protect police forces, private citizens and private security guards or...

, meant to intercept attacks, either by stopping projectiles such as arrow
Arrow
An arrow is a shafted projectile that is shot with a bow. It predates recorded history and is common to most cultures.An arrow usually consists of a shaft with an arrowhead attached to the front end, with fletchings and a nock at the other.- History:...

s or redirecting a hit from a sword
Sword
A sword is a bladed weapon used primarily for cutting or thrusting. The precise definition of the term varies with the historical epoch or the geographical region under consideration...

, mace or battle axe
Battle axe
A battle axe is an axe specifically designed for combat. Battle axes were specialized versions of utility axes...

 to the side of the shield-bearer.

Shields vary greatly in size, ranging from large panels that protect the user's entire body to small models (such as the buckler
Buckler
A buckler is a small shield, 15 to 45 cm in diameter, gripped in the fist; it was generally used as a companion weapon in hand-to-hand combat during the Medieval and Renaissance, as its size made it poor protection against missile weapons but useful in deflecting the blow of...

) that were intended for hand-to-hand-combat use. Shields also vary a great deal in thickness; whereas some shields were made of relatively deep, absorbent, wooden planking to protect soldiers from the impact of spear
Spear
A spear is a pole weapon consisting of a shaft, usually of wood, with a pointed head.The head may be simply the sharpened end of the shaft itself, as is the case with bamboo spears, or it may be made of a more durable material fastened to the shaft, such as flint, obsidian, iron, steel or...

s and crossbow
Crossbow
A crossbow is a weapon consisting of a bow mounted on a stock that shoots projectiles, often called bolts or quarrels. The medieval crossbow was called by many names, most of which derived from the word ballista, a torsion engine resembling a crossbow in appearance.Historically, crossbows played a...

 bolts, others were thinner and lighter and designed mainly for deflecting blade strikes.

In prehistory and during the era of the earliest civilizations, shields were made of wood, animal hide, woven reeds or wicker. In classical antiquity, the Migration Period
Migration Period
The Migration Period, also called the Barbarian Invasions , was a period of intensified human migration in Europe that occurred from c. 400 to 800 CE. This period marked the transition from Late Antiquity to the Early Middle Ages...

 and the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, they were normally constructed of poplar, lime or another split-resistant timber—covered in some instances with leather and/or reinforced with a metal boss
Boss (architecture)
In architecture, a boss is a knob or protrusion of stone or wood.Bosses can often be found in the ceilings of buildings, particularly at the intersection of a vault. In Gothic architecture, such roof bosses are often intricately carved with foliage, heraldic devices or other decorations...

, rim or banding—and carried by foot soldiers, knights and cavalry.

Shape wise, depending on time and place, shields could be round, oval, square, rectangular, triangular or scalloped. Sometimes they took on the form of kites, flatirons or figures-of-eight, or had rounded tops on a rectangular base with perhaps an eyehole inserted. The shield was held by a central grip or by straps which went over or around the user's arm

Often shields were decorated with a painted pattern or an animal representation and these designs developed into systematized heraldic devices during high-medieval times for purposes of battlefield identification. Even after the introduction of gunpowder and firearms to the battlefield, shields continued to be used by certain groups. In the 18th century, for example, Scottish Highland fighters liked to wield small shields (known as a targe
Targe
Targe was a general word for shield in late Old English. Its diminutive, target, came to mean an object to be aimed at in the 18th century....

), and as late as the 19th century, some non-industrialized peoples employed them (such as Zulu
Zulu Kingdom
The Zulu Kingdom, sometimes referred to as the Zulu Empire or, rather imprecisely, Zululand, was a monarchy in Southern Africa that extended along the coast of the Indian Ocean from the Tugela River in the south to Pongola River in the north....

 warriors) when waging war.

In the 20th and 21st century, shields have been used by military and police units that specialize in anti-terrorist actions, hostage rescue, riot control and siege-breaking. The modern term usually refers to a device that is held in the hand or attached to the arm, as opposed to an armored suit or a bullet-proof vest.

Prehistory and antiquity

The oldest form of shield was a protection device designed to block attacks by hand weapons, such as swords, axes and maces, or missile
Ranged weapon
A ranged weapon is any weapon that can harm targets at distances greater than hand-to-hand distance. In contrast, a weapon intended to be used in man-to-man combat is called a melee weapon....

s like javelins, sling-stones and arrows. Shields have varied greatly in construction over time and place. Sometimes shields were made of metal, but wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 or animal hide construction was much more common; wicker
Wicker
Wicker is hard woven fiber formed into a rigid material, usually used for baskets or furniture. Wicker is often made of material of plant origin, but plastic fibers are also used....

 and even turtle shells have been used. Many surviving examples of metal shields are generally felt to be ceremonial rather than practical, for example the Yetholm-type shields
Yetholm-type shields
Yetholm-type shields were used in 1200-800 BC . The known shields come from Britain and Ireland, excepting one from Denmark. Their modern name comes from Yetholm in southern Scotland where a peat bog yielded three examples of the approximately 20 known. The shields vary significantly in size, but...

 of the Bronze Age
Bronze Age
The Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...

 or the Iron Age
Iron Age
The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...

 Battersea shield
Battersea Shield
The Battersea Shield is one of the most significant pieces of ancient Celtic military equipment found in Britain. It is a sheet bronze covering of a wooden shield decorated in La Tène style...

. The shield was used to make the Greek Phalanx formation
Phalanx formation
The phalanx is a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar weapons...

.

Size and weight varied greatly. Lightly armored warriors
Light infantry
Traditionally light infantry were soldiers whose job was to provide a skirmishing screen ahead of the main body of infantry, harassing and delaying the enemy advance. Light infantry was distinct from medium, heavy or line infantry. Heavy infantry were dedicated primarily to fighting in tight...

 relying on speed and surprise would generally carry light shields that were either small or thin. Heavy troops
Heavy infantry
Heavy infantry refers to heavily armed and armoured ground troops, as opposed to medium or light infantry, in which the warriors are relatively lightly armoured. As modern infantry troops usually define their subgroups differently , 'heavy infantry' almost always is used to describe pre-gunpowder...

 might be equipped with robust shields that could cover most of the body. Many had a strap called a guige
Guige
A guige is a long strap, typically made of leather, used to hang a shield on the shoulder or neck. This technique was primarily done when the shield was not in use...

 that allowed it to be slung over the user's back when not in use or on horseback. During the 14th-13th century BC, the Sards or Shardana, working as mercenaries for the Egyptian pharaoh Ramses II, utilized either large or small round shields against the Hittites
Hittites
The Hittites were a Bronze Age people of Anatolia.They established a kingdom centered at Hattusa in north-central Anatolia c. the 18th century BC. The Hittite empire reached its height c...

. The Mycenaean Greeks
Mycenaean Greece
Mycenaean Greece was a cultural period of Bronze Age Greece taking its name from the archaeological site of Mycenae in northeastern Argolis, in the Peloponnese of southern Greece. Athens, Pylos, Thebes, and Tiryns are also important Mycenaean sites...

 used two types of shields: the "figure eight" or "fiddle" shield, and a rectangular type, the "tower" shield, curved on the top. They were made of wood and leather, and were of such a large size that a warrior could hide completely behind his shield. The Ancient Greek hoplites used a round, bowl-shaped wooden shield called an aspis
Aspis
"Aspis" is the generic term for the word shield. The aspis, which is carried by Greek infantry of various periods, is often referred to as a hoplon .According to Diodorus Siculus:-Construction:...

. Examples of Germanic wooden shields c350 BC - 500 AD survive from weapons sacrifice
Weapons sacrifice
The Greeks and Romans set up trophies after victories in battle. These have left little archaeology . Normally, on dry land wood will rot, iron will rust and bronze would be reused...

s in Danish bogs.

The heavily armored Roman legionaries carried large shields (scuta
Scutum (shield)
Scutum is the Latin word for "shield", although it has in modern times come to be specifically associated with the rectangular, semi-cylindrical body shield carried by Roman legionaries.-History:...

) that could provide far more protection, but made swift movement a little more difficult. The scutum originally had an oval shape, but gradually the curved tops and sides were cut to produce the familiar rectangular shape most commonly seen in the early Imperial legions. Famously, the Romans used their shields to create a tortoise-like formation called a testudo
Testudo formation
In Ancient Roman warfare, the testudo or tortoise formation was a formation used commonly by the Roman Legions during battles, particularly sieges. Testudo is the Latin word for "tortoise"...

 in which entire groups of soldiers would be enclosed in an armoured box to provide protection against missiles. Many ancient shield designs featured incuts of one sort of another. This was done to accommodate the shaft of a spear, thus facilitating tactics requiring the soldiers to stand close together forming a wall of shields
Shield wall
The wall, is a military tactic that was common in many cultures in the Pre-Early Modern warfare age...

.

Middle Ages

In the early Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, simple round shields made from linden-wood wood were typical. Over time, these were displaced by the kite shield
Kite shield
A kite shield was a distinct type of shield from the 10th–12th centuries. It was either a reverse teardrop shape or later on, flat-topped. The tapering point extended down to either a distinct or rounded point...

, which was rounded at the top and tapered at the bottom. This gave protection to the user's legs, without adding to the total weight of the shield. Kite shields were commonly used by cavalry as well.

As body armour improved, knight
Knight
A knight was a member of a class of lower nobility in the High Middle Ages.By the Late Middle Ages, the rank had become associated with the ideals of chivalry, a code of conduct for the perfect courtly Christian warrior....

's shields became smaller, leading to the familiar heater shield
Heater shield
The heater shield or heater-shaped shield is a form of European medieval shield, developing from the early medieval kite shield in ca. the mid 13th century....

 style. Both kite and heater style shields were made of several layers of laminated wood, with a gentle curve in cross section. The heater style inspired the shape of the symbolic heraldic shield that is still used today. Eventually, specialised shapes were developed such as the bouche, which had a lance
Lance
A Lance is a pole weapon or spear designed to be used by a mounted warrior. The lance is longer, stout and heavier than an infantry spear, and unsuited for throwing, or for rapid thrusting. Lances did not have tips designed to intentionally break off or bend, unlike many throwing weapons of the...

 rest cut into the upper corner of the lance side, to help guide it in combat or tournament. Free standing shields called pavise
Pavise
A pavise is a large convex shield of European origin used to protect the entire body. The pavise was also made in a smaller version for hand to hand combat and for wearing on the back of men-at-arms. It is characterized by its prominent central ridge...

s, which were propped up on stands, were used by medieval crossbow
Crossbow
A crossbow is a weapon consisting of a bow mounted on a stock that shoots projectiles, often called bolts or quarrels. The medieval crossbow was called by many names, most of which derived from the word ballista, a torsion engine resembling a crossbow in appearance.Historically, crossbows played a...

men who needed protection while reloading.

In time, some armoured foot knights gave up shields entirely in favour of mobility and two-handed weapons. Other knights and common soldiers adopted the buckler
Buckler
A buckler is a small shield, 15 to 45 cm in diameter, gripped in the fist; it was generally used as a companion weapon in hand-to-hand combat during the Medieval and Renaissance, as its size made it poor protection against missile weapons but useful in deflecting the blow of...

 (origin of the term "swashbuckler
Swashbuckler
Swashbuckler or swasher is a term that emerged in the 16th century and has been used for rough, noisy and boastful swordsmen ever since. A possible explanation for this term is that it derives from a fighting style using a side-sword with a buckler in the off-hand, which was applied with much...

"). The buckler is a small round shield, typically between 8 and 16 inches (20-40 centimeters) in diameter. The buckler was one of very few types of shield that were usually made of metal. Small and light, the buckler was easily carried by being hung from a belt; it gave little protection from missiles and was reserved for hand-to-hand combat. The buckler continued in use well into the 16th Century.

In Italy, the targa
Targe
Targe was a general word for shield in late Old English. Its diminutive, target, came to mean an object to be aimed at in the 18th century....

, parma
Parma (shield)
Parma or parmula was a type of round shield used by the Roman army, especially during the later period of Imperial history.-Characteristics:...

 and rotella were utilized by common people, fencers and even knights. The development of plate armour made shields less and less common as plate armour eliminated the need for a shield. Lightly armoured troops continued to use shields after men-at-arms and knights ceased to use them. Shields continued in use even after gunpowder
Gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...

 powered weapons made them essentially obsolete on the battlefield. In the 18th Century, the Scottish clans used a small, round shield called a targe
Targe
Targe was a general word for shield in late Old English. Its diminutive, target, came to mean an object to be aimed at in the 18th century....

 that was partially effective against the firearms of the time, although it was arguably more often used against British infantry bayonets and cavalry swords in close-in fighting.

During the 19th Century, non-industrial cultures with little access to guns were still using war shields. Zulu
Zulu Kingdom
The Zulu Kingdom, sometimes referred to as the Zulu Empire or, rather imprecisely, Zululand, was a monarchy in Southern Africa that extended along the coast of the Indian Ocean from the Tugela River in the south to Pongola River in the north....

 warriors carried large lightweight shields made from a single ox hide supported by a wooden spine, these were called Ishlangu. This was used in combination with a short spear (assegai
Assegai
An assegai or assagai is a pole weapon used for throwing or hurling, usually a light spear or javelin made of wood and pointed with iron.-Iklwa:...

) and/or club
Club (weapon)
A club is among the simplest of all weapons. A club is essentially a short staff, or stick, usually made of wood, and wielded as a weapon since prehistoric times....

.

Although the size of shield would vary due to personal preference and role, most were thin compared to common belief (a misconception aided by the depiction of heavy shields in films). When used in fighting, shields were most effective when used to cause glancing blows. By deflecting a sword blow to the side, rather than blocking it head on, the attacker could be rendered open to a counterattack. This technique allowed the shield to be made lighter and more easily wielded, while reducing the amount of energy and risk of injury posed to the shied-bearer.

Law enforcement shields

Shields for protection from armed attack are still used by many police
Police
The police is a personification of the state designated to put in practice the enforced law, protect property and reduce civil disorder in civilian matters. Their powers include the legitimized use of force...

 forces around the world. These modern shields are usually intended for two broadly distinct purposes. The first type, riot shield
Riot shield
Riot shields are lightweight protection devices deployed by police and some military organizations. Most are a clear polycarbonate, though some are constructed of light metals with a view hole. Riot shields are almost exclusively long enough to cover an average sized man from the top of the head to...

s, are used for riot control
Riot control
Riot control refers to the measures used by police, military, or other security forces to control, disperse, and arrest civilians who are involved in a riot, demonstration, or protest. Law enforcement officers or soldiers have long used non-lethal weapons such as batons and whips to disperse crowds...

 and can be made from metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 or polymers such as polycarbonate Lexan
Lexan
Lexan is a registered trademark for SABIC Innovative Plastics' brand of polycarbonate resin thermoplastic. Polycarbonate polymer is produced by reacting bisphenol A with carbonyl dichloride, also known as phosgene. Lexan is the brand name for polycarbonate sheet and resin in a wide range of grades...

 or Makrolon or boPET Mylar. These typically offer protection from relatively large and low velocity projectiles, such as rocks and bottles, as well as blows from fists or clubs. Synthetic riot shields are normally transparent, allowing full use of the shield without obstructing vision. Similarly, metal riot shields often have a small window at eye level for this purpose. These riot shields are most commonly used to block and push back crowds when the users stand in a "wall" to block protesters, and to protect against shrapnel
Fragmentation (weaponry)
Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...

, projectiles, molotov cocktails, and during hand-to-hand combat.

The second type of modern police shield is the bullet-resistant tactical shield. These shields are typically manufactured from advanced synthetics such as kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...

 and are designed to be bulletproof
Bulletproof
Bulletproofing is the process of making something capable of stopping a bullet or similar high velocity projectiles e.g. shrapnel. The term bullet resistance is often preferred because few, if any, practical materials provide complete protection against all types of bullets, or multiple hits in the...

, or at least bullet resistant. Tactical shields often have a firing port so that the officer holding the shield can fire a weapon while being protected by the shield, and they often have a bulletproof glass viewing port. They are typically employed by specialist police, such as SWAT
SWAT
A SWAT team is an elite tactical unit in various national law enforcement departments. They are trained to perform high-risk operations that fall outside of the abilities of regular officers...

 teams in high risk entry and siege scenarios, such as hostage rescue and breaching gang compounds, as well as in antiterrorism operations. Tactical shields often have a large signs stating "POLICE" (or the name of a force, such as "US MARSHALS") to indicate that the user is a law enforcement officer.

Gun shields

With the widespread use of machine guns in World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 and in subsequent conflicts, battlegrounds were swept with automatic weapons fire. While soldiers who are in foxholes or trenches are protected from this fire, soldiers who are manning mounted machine guns were vulnerable to being hit. Since WW I, there have been a variety of attempts to install armored gun shields on tripod-mounted machine guns or vehicle-mounted weapons to protect machine gunners. Transportation devices with mounted guns that may have gun shields to protect the gunner include jeeps, Humvees, armored cars, and boats.

Non-martial applications

Many non-martial devices also employ shielding of a kind—not usually a single device worn on an arm but various protective plates or other insulation positioned where needed. Space craft have heat shields to ensure a safe re-entry
Atmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...

. Electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 uses shielding to reduce electrical noise and crosstalk between signals. Better-quality patch cables used in audio and electronic music have shielding to reduce interference and noise. People and systems that must work in the presence of ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...

 (X-rays) such as dentists, hospital technicians, and patients undergoing X-rays are protected with lead shielding clothing.

A "shield" is also a design term used to describe emblems that resemble a heraldic shield. Movie studio Warner Bros.
Warner Bros.
Warner Bros. Entertainment, Inc., also known as Warner Bros. Pictures or simply Warner Bros. , is an American producer of film and television entertainment.One of the major film studios, it is a subsidiary of Time Warner, with its headquarters in Burbank,...

 uses a shield emblazoned with WB as its logo. The Looney Tunes
Looney Tunes
Looney Tunes is a Warner Bros. animated cartoon series. It preceded the Merrie Melodies series and was Warner Bros.'s first animated theatrical series. Since its first official release, 1930's Sinkin' in the Bathtub, the series has become a worldwide media franchise, spawning several television...

 cartoons, released through Warner Bros., open with the WB shield zooming through concentric circle
Circle
A circle is a simple shape of Euclidean geometry consisting of those points in a plane that are a given distance from a given point, the centre. The distance between any of the points and the centre is called the radius....

s.

See also

  • Aspis
    Aspis
    "Aspis" is the generic term for the word shield. The aspis, which is carried by Greek infantry of various periods, is often referred to as a hoplon .According to Diodorus Siculus:-Construction:...

  • Buckler
    Buckler
    A buckler is a small shield, 15 to 45 cm in diameter, gripped in the fist; it was generally used as a companion weapon in hand-to-hand combat during the Medieval and Renaissance, as its size made it poor protection against missile weapons but useful in deflecting the blow of...

  • Heater shield
    Heater shield
    The heater shield or heater-shaped shield is a form of European medieval shield, developing from the early medieval kite shield in ca. the mid 13th century....

  • Kite shield
    Kite shield
    A kite shield was a distinct type of shield from the 10th–12th centuries. It was either a reverse teardrop shape or later on, flat-topped. The tapering point extended down to either a distinct or rounded point...

  • Scutum (shield)
    Scutum (shield)
    Scutum is the Latin word for "shield", although it has in modern times come to be specifically associated with the rectangular, semi-cylindrical body shield carried by Roman legionaries.-History:...

  • Escutcheon (heraldry)

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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