Mathee Pongkitwitoon และ Watcharin Klongdee. (2016) Using GM(1,1) with sample standard deviation to forecast downtrend rainfall for small sample in Khon Kaen, Thailand. <i>KKU Engineering Journal</i>, <i>43</i>(S1), 111-113.Mathee Pongkitwitoon และ Watcharin Klongdee. "Using GM(1,1) with sample standard deviation to forecast downtrend rainfall for small sample in Khon Kaen, Thailand". KKU Engineering Journal 43 (2016):111-113.Mathee Pongkitwitoon และ Watcharin Klongdee. Using GM(1,1) with sample standard deviation to forecast downtrend rainfall for small sample in Khon Kaen, Thailand. Faculty of Engineering, Khon Kaen University:ม.ป.ท. 2016.