Koufopantelis P, Georgakakou S, Kazanis M, Giaginis C, Margeli A, Papargiri S, Panderi I. Direct injection liquid chromatography/positive ion electrospray ionization mass spectrometric quantification of methotrexate, folinic acid, folic acid and ondansetron in human serum. Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences [Internet]. 2009;877:3850 – 3856.