1. The ‘crowding-out’ effect of governmental transfers on private charitable contributions;Abrams;Public Choice,1978
2. Americans Volunteer, 1981 (The Gallup Organization, for Independent Sector, Princeton, New Jersey).
3. Americans Volunteer, 1985 (The Gallup Organization, for Independent Sector, Princeton, New Jersey).
4. Human Capital;Becker,1975
5. The measurement of United States real capital input, 1929–1967;Christensen;Review of Income and Wealth Series,1969