Duke University Press,
Majalah, Jurnal, Buletin
Short, Raymond W.
Henry Holt and Company, 1954
Buku Teks SO
Wachner, Clarence W.
Macmillan, 1963
Buku Teks SO
edited by Sculley Bradley, Richmond Croom Beatty and E. Hudson Lon
W.W. Norton, 1967
Buku Teks SO
Abel, Darrel
Barron's Educational Series, 1963
Buku Referensi