Haviland, Virginia, author
Scott, Foresman, 1973
Buku Teks
Grolier Incorporated, 1997
Buku Referensi
Carlsen, G. Robert
Harper & Row, 1971
Buku Referensi
Hatt, Frank, author
Clive Bingley, 1986
Buku Teks
Martin Montgomery ... [and others]
Routledge , 2007
Buku Teks