Bernice E. Cullinan, Roger C. Farr, W. Dorsey Hammond, Nancy L. Roser, Dorothy S. Strickland
Harcourt Brace Jovanovich, Publishers, 1989
Buku Teks SO
Scholastic, 1982
Buku Teks SO
by Martha Dallmann ... [et al.]
Holt, Rinehart and Winston, 1982
Buku Teks
Artikel Jurnal
Tinker, Miles A.
Appleton-Century-Crofts, 1962
Buku Teks