Vacharotayan, Sorasith, Somjet Chantawat, Pojanee Laopairoj, and Ying Vacharacoop. 1964. “Preliminary Evaluation of Different Chemical Soil Test Methods for Available Phosphorus through Correlation with Greenhouse Test1”. Agriculture and Natural Resources 4 (3&4). Bangkok, Thailand:97-109. https://li01.tci-thaijo.org/index.php/anres/article/view/240124.