Kanokporn Bunnumma. (1989) The study on humic acid extraction from peat and its application to the paddy field. Mahidol University,:ม.ป.ท.Kanokporn Bunnumma. 1989. The study on humic acid extraction from peat and its application to the paddy field. ม.ป.ท.:Mahidol University,;Kanokporn Bunnumma. The study on humic acid extraction from peat and its application to the paddy field. ม.ป.ท.:Mahidol University, 1989. Print.