 After his retirement, he was president of the Institute for Financial Crime Prevention, a foundation for the research of white-collar crime.He served as a consultant on organized crime for the President's Commission on Law Enforcement and Administration of Justice in 1966 and 1967.Based on research conducted in this capacity he wrote the acclaimed "Theft of the Nation," a treatise on the Cosa Nostra, and later the smaller "Criminal Organization," in which he extended his conceptualization of organized crime to include criminal groups other than the Cosa Nostra.