Duke University Press,
Majalah, Jurnal, Buletin
Wachner, Clarence W.
Macmillan, 1963
Buku Teks SO
edited by Randall Stewart and Dorothy Bethurum
Scott, Foresman, 1954
Buku Teks SO
Abel, Darrel
Barron's Educational Series, 1963
Buku Referensi
Compiled and edited by Dorothy Nyren Curley, Maurice Kramer, Elaine Fialka Kramer
Continuum, 1989
Buku Referensi