QIAN, B., PANICHAYUPAKARANANT, P., SIRIKATITHAM, A., ZHANG, R., GUO, Y. and WU, Y. 2005. Quantitative HPLC determination of indigotin and indirubin in indigo naturalis. Ars Pharmaceutica (Internet). 46, 4 (Sep. 2005), 429–438.