Narongsak Singhunt และผู้แต่งคนอื่นๆ. (2019) Training Needs on Land Development of Sub-District Volunteer Soil Doctors in Udon Thani Province. <i>Khon Kaen Agriculture Journal</i>, <i>47</i>(4), 773-786.Narongsak Singhunt และผู้แต่งคนอื่นๆ. "Training Needs on Land Development of Sub-District Volunteer Soil Doctors in Udon Thani Province". Khon Kaen Agriculture Journal 47 (2019):773-786.Narongsak Singhunt และผู้แต่งคนอื่นๆ. Training Needs on Land Development of Sub-District Volunteer Soil Doctors in Udon Thani Province. Faculty of Agriculture:ม.ป.ท. 2019.