Edward Elgar, 1997
Buku Teks
edited by Gunther Schmid, Jacqueline O'Reilly and Klaus Schomann
Edward Elgar, 1996
Buku Referensi
Gupta, Anand P., author
McGraw-Hill, 1977
Buku Teks
Puguh B. Irawan
International Labour Office , 2000
Buku Teks
Song, Yang, author
Blackwell Publishing, 2017
Artikel Jurnal