Ratanasthien, K. “FOLIC ACID ANTAGONISTS (THE DIHYDROFOLATE REDUCTASE INHIBITORS): APPLICATION OF TETRAZOLIUM BIOAUTOGRAPHY ON DETERMINATION OF SERUM AND URINE METHOTREXATE”. Journal of Associated Medical Sciences, vol. 9, no. 2, June 2016, p. 107, https://he01.tci-thaijo.org/index.php/bulletinAMS/article/view/60842.