Kovacs, Diane K.
Facet Publishing, 2007
Buku Referensi
Kern, M. Kathleen
American Management Association, 2009
eBooks
Cassell, Kay Ann
Neal-Schuman, an imprint of the American Library Association, 2013
Buku Teks SO
edited by Bill Katz and Ruth A. Fraley
Haworth Press, 1984
Buku Referensi
Rifni Raihana
Fakultas Ilmu Pengetahuan Budaya Universitas Indonesia, 2017
UI - Skripsi Open