Keylor, William R., 1944-
Oxford University Press, 1996
Buku Teks SO
edited by Alexander Baltzly, A. William Salomone
Appleton-Century-Crofts, 1950
Buku Teks SO
Palmer, Alan
Penguin Books , 1987
Buku Referensi
Kragh, Helge
Princeton University press, 1999
Buku Teks SO
edited by Alexander Baltzly
Appleton-Century-Crofts, Inc, 1950
Buku Teks SO