Becker, Esther R., author
Harper & Row, 1971
Buku Referensi
Doris, Lillian, author
Prentice-Hall, 1970
Buku Referensi
Boston: Houghton: 1993,
Buku Referensi
De Vries, Mary Ann, author
Prentice-Hall, 1991
Buku Referensi
Bredow, Miriam
McGraw-Hill, 1964
Buku Teks