Orley Ashenfelter and Richard Layard (eds.) "Handbook of Labor Economics vol. 1" Elsevier Science, 1986 Orley Ashenfelter and Richard Layard (eds.) "Handbook of Labor Economics vol. 2" Elsevier Science, 1986 Orley Ashenfelter and David Card (eds.) "Handbook of Labor Economics vol. 3A-3C" Elsevier Science, 1999