Regional differences in waiting time to pregnancy among fertile couples from four European cities

Tina Kold-Jensen, Remy Slama, B. Ducot, J. Suominen, Elizabeth H.H. Cawood, A. G. Andersen, Florence Eustache, S. Irvine, S. Auger, P. Jouannet, Matti Vierula, N. Jørgensen, Jorma Toppari, Niels Erik Skakkebæk, Niels Keiding, Alfred Spira