N. WADIA, D., and H. T. DESAI. “ULTRA PERFORMANCE LIQUID CHROMATOGRAPHY (UPLC) METHOD DEVELOPMENT AND VALIDATION FOR THE SIMULTANEOUS ESTIMATION OF ETOPHYLLINE AND THEOPHYLLINE IN PHARMACEUTICAL DOSAGE FORM: Pharmaceutical Science-Analytical Chemistry”. International Journal of Life Science and Pharma Research, vol. 2, no. 3, Sept. 2012, pp. P19-P24, https://ijlpr.com/index.php/journal/article/view/245.