Eiteman, David K., author
Pearson, 2019
Buku Teks
Eiteman, David K., author
Erlangga, 2010
Buku Teks
Lubis, Todung Mulya, author
Universitas Indonesia, 1977
Buku Teks
International Labur Organization, 1992
Buku Teks
Thomas, Spencer
East Sussex Wayland , 1979
Buku Teks