Ruengsitagoon, Wirat, and Chantana Aromdee. 2017. “Determination of lead, copper, zinc and iron in centella asiatica by atomic absorption spectrophotometry (Thai)”. Asia-Pacific Journal of Science and Technology 14 (5):412-20. https://so01.tci-thaijo.org/index.php/APST/article/view/83452.