Description based on: Embryonal stem cells : introducing planned changes into the animal germline / Martin L. Hooper, Volume 1, copyrighted 1992; title from series page (amazon.com website, viewed July 24, 2017).
2:
Latest issue consulted: Genetics of steroid biosynthesis and function / edited by J.I. Mason, Volume 6, copyrighted 2002 (viewed Oct. 30, 2017).