Montague, Harriet F.
Charles E. Merrill, 1963
Buku Teks SO
Artikel Jurnal
Morant, G.M.
Unesco, 1952
Buku Teks SO
edited with introductions by Michael Bromley, Tom O'Malley
Routledge , 1997
Buku Teks
Fjeldstad, Mary C.
Harcourt Brace College Publisher, 1998
Buku Teks