“Simultaneous Determination of Azathioprine and Its Metabolite 6-Mercaptopurine in Human Plasma Using Solid Phase Extraction-Evaporation and Liquid chromatography–positive Electrospray Tandem Mass Spectrometry”. 2012. International Current Pharmaceutical Journal 1 (11): 342-52. https://doi.org/10.3329/icpj.v1i11.12059.