Morton, Joyce, author
Prentice-Hall, 1998
Buku Teks
Doris, Lillian
Prentice-Hall, 1960
Buku Teks
Jennings, Lucy Mae
Prentince-Hall, 1983
Buku Teks
Ochs, Linnea Leedham, author
Prentice-Hall, 1987
Buku Referensi
edited by Coleen K. Withgott, Austin G. Anderson
Merriam-Webster, 1981
Buku Referensi