Proponents of a graduated concept of protection are e.g.:

Lockwood, M. (1985). The Warnock Report: a philosophical appraisal. In Lockwood, M. (Ed.). Moral Dilemmas in Modern Medicine, 153-186. Oxford University Press.

Sass, H. (1989). Hirntod und Hirnleben. In ders. (Hrsg.). Medizin und Ethik, 160–183. Reclam.