(Inggris)"On the role of transforming growth factor-β in the growth inhibitory effects of retinoic acid in human pancreatic cancer cells". Department of Surgery and Robert H Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Department of Biomedical Sciences, Creighton University, Department of Physiology, Faculty of Medicine and Health Sciences, United Arab Emirates University; Brahmchetna Singh, Richard F Murphy, Xian-Zhong Ding, Alexandra B Roginsky, Richard H Bell, Jr, dan Thomas E Adrian. Diakses tanggal 2010-12-08.