Supattra Somapa. (1994) Serum melatonin levels in human subjects from the Northeastern and central parts of Thailand. Mahidol University,:ม.ป.ท.Supattra Somapa. 1994. Serum melatonin levels in human subjects from the Northeastern and central parts of Thailand. ม.ป.ท.:Mahidol University,;Supattra Somapa. Serum melatonin levels in human subjects from the Northeastern and central parts of Thailand. ม.ป.ท.:Mahidol University, 1994. Print.