Natta Takrattanasaran, Jongruk Chanchareonsook, Suthep Thongpae and Ed Sarobol 2010. Evaluation of Mehlich 3 and Ammonium Bicarbonate-DTPA Extractants for Prediction of Available Zinc in Calcareous Soils in Central Thailand. Agriculture and Natural Resources. 44, 5 (Oct. 2010), 824–829.