Biao และ Yang. (1991) Factors affecting the village headmen's knowledge and attitude in promoting water supply in Kamphaeng Phet province of Thailand. Mahidol University,:ม.ป.ท.Biao และ Yang. 1991. Factors affecting the village headmen's knowledge and attitude in promoting water supply in Kamphaeng Phet province of Thailand. ม.ป.ท.:Mahidol University,;Biao และ Yang. Factors affecting the village headmen's knowledge and attitude in promoting water supply in Kamphaeng Phet province of Thailand. ม.ป.ท.:Mahidol University, 1991. Print.