DIXIT HETAL B, SINGH SHWETA D, BALDANIYA SUNIL L, SHAH DIMAL A, MEHTA FALGUN A, and CHHALOTIYA USMANGANI K, “DEVELOPMENT AND VALIDATION OF STABILITY INDICATING RP-HPLC METHOD FOR LEVONORGESTREL IN PHARMACEUTICAL DOSAGE FORM”, IJPDA, vol. 2, no. 7, pp. 553-566, Jul. 2014.