Akaruese, Lucky
Xlibris Corporation, 2012
Buku Teks SO
edited by Eric Delson, Ian Tattersall, John A. Van Couvering and Alison S. Brokks
Garland Publishing, 2000
Buku Referensi
McKee, Jeffrey K.
Pearson/Prentice Hall, 2005
Buku Teks
Eckhardt, Robert B.
McGraw-Hill, 1979
Buku Teks
Pawson, Ivan G.
John Wiley & Sons, 1977
Buku Teks