Hoffmann R and Lipscomb WN, Theory of Polyhedral Molecules. I. Physical Factorizations of the Secular Equation, J. Chem. Phys., 36, 2179 (1962). Hoffmann R and
Budapest 1967 xi+373 pp. Béla Szőkefalvi-Nagy, Frederic Riesz: Funkcionálanalízis. Budapest, 1988. 534 p. (English: Functional Analysis (1990). Dover. ISBN 0-486-66289-6)