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

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

Sass, Hans-Martin (1989): Hirntod und Hirnleben. In: Leist, Anton (ed.): Medizin und Ethik. Stuttgart: Reclam, 160-183.