D. Mansour u. a.: Efficacy and tolerability of a monophasic combined oral contraceptive containing nomegestrol acetate and 17 β -oestradiol in a 24/4 regimen, in comparison to an oral contraceptive containing ethinylestradiol and drospirenone in a 21/7 regimen. In: The European Journal of Contraception and Reproductive Health Care. 2011. PMID 21995590.