Edwards, I.E.S.
Penguin Books, 1947
Buku Teks SO
Hodges, Peter
Aris & Phillips, 1993
Buku Referensi
Ashton, Sally-Ann
Blackwell Publishing, 2008
Buku Teks SO
Casson, Lionel
Time-Life Books, 1965
Buku Teks SO
Bard, Kathryn A.
Blackwell Publishing, 2008
Buku Teks SO