1. Alpert, William T. “Unions and Private Wage Supplements.”Journal of Labor Research 3 (Spring 1982): 179–99.
2. Bureau of Labor Statistics (BLS), U.S. Department of Labor.Employee Compensation in the Private Nonfarm Economy 1970, Bulletin 1770. Washington, D.C.: Government Printing Office, 1973.
3. _____.Employee Benefits in Medium and Large Firms, 1989. Bulletin 2363, Washington, D.C.: Government Printing Office, 1990.
4. Cragg, John G. “Some Statistical Models for Limited Dependent Variables with Application to the Demand for Durable Goods.”Econometrica 39 (September 1971): 829–44.
5. Duncan, Greg J., and Frank P. Stafford. “Do Union Members Receive Compensating Wage Differentials?”American Economic Review 70 (June 1980): 355–71.