Wagstaff, Liz, author
Quadrille, 1999
Buku Referensi
International Labour Organization
International Labour Organization, 1994
Buku Teks
Springer, 2017
Buku Teks
edited by J. Fred Weston
Holt, Rinehart and Winston, 1966
Buku Teks
Hepner, Harry W., author
Prentice-Hall, 1971
Buku Teks