Soontrapa, Suppasin, Sukree Soontrapa, and La-Or Chailurkit. 2013. “The Difference in Vitamin D Status Between Urban and Rural Elderly Women of Khon Kaen Province, Thailand”. Srinagarind Medical Journal 19 (2):67-74. https://li01.tci-thaijo.org/index.php/SRIMEDJ/article/view/14490.