Chatchai Ekpunyasakul. (2008) The History of Occupational Medicine. <i>Journal of Medicine and Health Sciences</i>, <i>14</i>(3), 152-166.Chatchai Ekpunyasakul. "The History of Occupational Medicine". Journal of Medicine and Health Sciences 14 (2008):152-166.Chatchai Ekpunyasakul. The History of Occupational Medicine. Faculty of Medicine,Srinakharinwirot University:ม.ป.ท. 2008.