- Low-dose oral contraceptives and acquired resistance to activated protein C: a randomised cross-over study. Rosing, J., Middeldorp, S., Curvers, J., Christella, M., Thomassen, L.G., Nicolaes, G.A., Meijers, J.C., Bouma, B.N., Büller, H.R., Prins, M.H., Tans, G. Lancet (1999)