Griniatsos J, Michail OP, Theocharis S, Arvelakis A, Papaconstantinou I, Felekouras E, Pikoulis E, Karavokyros I, Bakoyiannis C, Marinos G, et al. Circadian variation in expression of G1 phase cyclins D1 and E and cyclin-dependent kinase inhibitors p16 and p21 in human bowel mucosa. World J Gastroenterol. 2006;12(13):2109-14.