Appendix A: Sources and Methods, Human Capital: A Theoretical and Empirical Analysis, with Special Reference to Education, Second Edition

Gary S. Becker, Human Capital: A Theoretical and Empirical Analysis, with Special Reference to Education, Second Edition (NBER, 1975), https://www.nber.org/books-and-chapters/human-capital-theoretical-and-empirical-analysis-special-reference-education-second-edition/appendix-sources-and-methods-human-capital-theoretical-and-empirical-analysis-special-reference.