The work at Zhoukoudian was carried out under difficult conditions: for example, the scientists had to ride there on mules, some 40 km southwest of the city of Beijing.

The first fossil hominin skullcap was recovered by Pei "working in a 40-meter crevasse in frigid weather with a hammer in one hand and a candle in the other on December 2, 1929, at 16.00 hours (local).

[2] After Zhoukoudian, Pei worked at many other archaeological sites, including Djalainor (Zhalainu'er) in eastern Inner Mongolia and in Gansu.

[1] His cremated remains are interred behind the museum at the Zhoukoudian site alongside those of his colleagues, Yang Zhongjian and Jia Lanpo.

Palaeontologia Sinica, Geological Survey of China, Beijing PEI, W. C. (1934), REPORT ON THE EXCAVATION OF THE LOCALITY 13 IN CHOUKOUTIEN.