Traces of craftsmen's stamps on the famed Terracotta Warriors－signatures of the artisans－prove that the creation of the figures followed a "multichannel supply" model, according to research published recently in the journal Archaeometry.

"We've proved that the figures are works of art made by a team, and have further demonstrated that they are of great artistic value and not just a production-line model," said Xia Yin, an author of the geochemical study by British, Chinese and German scholars.

Xia, also director of the relics protection department at Emperor Qinshihuang's Mausoleum Site Museum, home of the Terracotta Warriors, said many artisans produced similar works during the Qin Dynasty (221-206 BC), and parts of the warriors were produced in many different places.

"Gong" and "Xianyang" are both inscriptions left on the statues. When restoring them, the conservator-restorers would find some characters etched on the figures.

The study said "Gong" refers to craftsmen from the palace workshop of Qinshihuang, China's first emperor. They were chief experts with their own stamps, Xia said."They could have been responsible for elements requiring higher quality."

"Xianyang" refers to craftsmen from the Xianyang area in today's Shaanxi province, along with other skilled workers elsewhere, who provided additional elements, Xia said.

"Such multichannel supply chain management might be an example of economy of scale, allowing completion of the unprecedented project in a short time," he said.

Researchers found that components for each body part of the same warrior figure were similar, while components of other warriors have differences in the same body part, indicating that different figures were probably made by different, independent workshops.

"In the early stages, academics speculated that production of the Terracotta Warriors might have involved a sort of modularization, meaning that many of the arms, legs, heads and other parts of the body would be mass-produced," Xia said. "Our recent analysis found that the components of a dozen parts of a figure are relatively the same, but differences are found when they are compared with other figures."

To find out the production patterns, the group used portable X-ray fluorescence spectrometers to examine 28 warriors in the pit of Terracotta Army No 1 at the mausoleum site museum in Xi'an, Shaanxi province.

"Relevant geochemical data was acquired, and our research team conducted further statistical analysis," Xia said.

Zhou Ping, deputy director of the site museum, said that in recent years the museum has used advanced analysis and technologies to strengthen the protection of the archaeological excavation.