Wheeler, Ruric E.
John Wiley & Sons, 1979
Buku Teks SO
Miller, Charles David, 1942-
Scott, Foresman and Co., 1978
Buku Teks SO
Hemming, 1998
Multimedia
Bergamini, David
Time Incorporated, 1963
Buku Referensi
Collier, Leonard Dawson
St. Paul's House Warwick Lane, 1973
Buku Teks SO