1. VON HENTIG, HANS, THE CRIMINAL AND His VICTIM, New Haven: Yale University Press, 1948, pp. 383–385.
2. TARDE, GABRIEL, PENAL PHILOSOPHY, Boston: Little, Brown, and Company, 1912, p. 466.
3. DE QUINCEY, T On Murder Considered as One of the Fine Arts,THE ARTS OF CHEATING, SWINDLING, AND MURDER, EDWARD BULWER-LYTTON AND DOUGLAS JERROLD, AND THOMAS DEQUINCEY New York: The Arnold Co., 1925, p. 153.
4. GAROFALO, BARON RAFFAELE, CRIMINOLOGY Boston: Little, Brown, and Company, 1914, p. 373.
5. For an excellent discussion of the rule of provocation, from which these four requirements are taken, see: ROLLIN M. PERKINS, The Law of Homicide,JOUR. Of CRIM. LAW AND CRIMINOL., (March-April, 1946), 36: 412–427; AND HERBERT WECHSLER AND JEROME MICHAEL, A RATIONALE OF THE LAW OF HOMOCIDE, pp. 1280–1282. A general review of the rule of provocation, both in this country and abroad, may be found in THE ROYAL COMMISSION ON CAPITAL PUNISHMENT, 1949–1952 Report,Appendix II, pp. 453–458.