How Population Size and Density Affect the Spread of COVID-19 A Quantitative Study of the United States at the County LevelQingyuan Li · First published 2021Open the Tome
清源山志Qingyuan Shi (China). Dian li gong ye ju. "Qingyuan dian li gong ye zhi" bian wei hui · First published 1999 · Latest edition 2013Open the Tome
Tan xun Zhongguo zi ben shi chang fa zhan zhi lu 1985-2005Qingyuan Li · First published 2006Open the Tome
