Lane, Mary Turner
Carolina Population Center, 1974
Buku Teks
Reilly, Dorothy E., author
Appleton-Century Crofts, 1978
Buku Teks
Turner, Alan (Alan E.)
Macmillan Education, 1990
Buku Teks
Mac Stravic, Robin E. Scott
Aspen Systems Corp., 1980
Buku Teks
Kapfer, Mirriam B.
Educational Technology Publication, 1972
Buku Teks