Wichuratree Klubseang และ Thanawat Jarupongsakul. (2010) Paleogeography and paleoenvironment of Nong Han Kumphawapi, Changwat Udon Thani. Chulalongkorn University:ม.ป.ท.Wichuratree Klubseang และ Thanawat Jarupongsakul. 2010. Paleogeography and paleoenvironment of Nong Han Kumphawapi, Changwat Udon Thani. ม.ป.ท.:Chulalongkorn University;Wichuratree Klubseang และ Thanawat Jarupongsakul. Paleogeography and paleoenvironment of Nong Han Kumphawapi, Changwat Udon Thani. ม.ป.ท.:Chulalongkorn University, 2010. Print.