Hedgecoe, John
Ebury, 1992
Buku Referensi
Dunne, Lavon J.
McGraw-Hill, 2001
Buku Teks SO
ed. by Howard S. Rowland
An Aspen publication , 1984
Buku Referensi
Hubbard, L. Ron, 1911-1986
Bridge Publications, Inc., 2012
Buku Referensi
Multi Kirana Pratama, 1997
Buku Referensi