Fertility and sterility Nachtigall R, Becker G, Tober D, Friese C, Butler A.. Parents' Conceptualization of their Frozen Embryos. Fertility and Sterility. 2003; 3(80):49. 2003 https://researcherprofiles.org/profile/1333939 Nachtigall R, Becker G, Tober D, Friese C, Butler A.