Kaufman, Scott Barry, author
Basic Books, Inc., 2013
Buku Teks
Thomson, Godfrey
Houghton Miffiln, 1956
Buku Teks
Heyel, Carl, author
American Management Association, 1958
Buku Teks
Yasmin Aulia Hayyu, author
Fakultas Ilmu Pengetahuan dan Budaya Universitas Indonesia, 2008
UI - Skripsi (Open)
Gorvernment printing Office , 1947
Buku Teks