00462nas a2200145   4500000000100000008004100001100001400042700001600056700001700072700001200089245018300101300001000284490000800294022001400302       2011                            d1 aL. Parkin1 aK. Sharples1 aR. Hernandez1 aS. Jick00aRisk of venous thromboembolism in users of oral contraceptives containing drospirenone or levonorgestrel: nested case-control study based on UK General Practice Research Database  ad21390 v342  a0959-8138