Tracy, Brian, author
American Management Association, 2004
eBooks
Andrew, author
Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Indonesia, 2012
UI - Skripsi Open
Szafran, Robert F.
Praeger , 1984
Buku Teks
Johnson, Luke, author
Penguin book, 2013
Buku Teks
Ismail, salim, author
Diversionbooks, 2014
Buku Teks