Scott F. Gilbert: Developmental Biology 8e Online: When Does Human Life Begin?. 8e.devbio.com. [dostęp 2010-03-28]. Cytat: ... One such discovery in the last twenty years is that research has shown that there is no "moment of fertilization" at all. Scientists now choose to view fertilization as a process that occurs over a period of 12-24 hours.(ang.).
