National Bureau of Economic Research., International Labour Office., Social Science Research Council (U.S.). Committee on Scientific Aspects of Human Migration., Willcox, W. F., Ferenczi, I., & Willcox, W. F. (1929). International migrations. New York.

National Bureau of Economic Research., International Labour Office, Social Science Research Council (U.S.). Committee on Scientific Aspects of Human Migration, Walter Francis Willcox, Imre Ferenczi, and Walter Francis Willcox. International Migrations. New York, 1929.

National Bureau of Economic Research., et al. International Migrations. New York, 1929.