1. Hubbard BAF, Karnofsky ES. In: Plato’s Protagorus: A Socratic Commentary. Chicago: University of Chicago Press; 1984:Book IX, Sect. 51.
2. For a fuller discussion of my views on the process of classification in medicine and the crucial and central role it plays in the genesis of hypotheses, planning of research, and diagnosis and treatment of patients, see the discussion in Chapter 1.
3. Silverman WA, Flynn JT, eds. Retinopathy of Prematurity. Boston: Blackwell Scientific; 1985: 1–18.