2002
- Leon R. Kass, "The Permanent Limitations of Biology" (2002) pdf
- Leon R. Kass, "The Permanent Limitations of Biology", chapter 10 of Leon R. Kass, Life, Liberty and the Defense of Dignity. The Challenge for Bioethics, Encounter Books, San Francisco 2002, s. 277-305.
- Leon R. Kass, "The Permanent Limitations of Biology" (2002)
- Catholic Educator's Resource Center; http://catholiceducation.org/articles/medical_ethics/me0052.html