Konopka, Gisela, author
Prentice-Hall, 1963
Buku Teks
Trecker, Harleigh B., author
Association Press, 1971
Buku Teks
Trecker, Harleigh B., author
Association Press, 1967
Buku Teks
Morales, Armando, author
Allyn and Bacon, 1983
Buku Teks
O`Sullivan, Terence, author
Macmillan, 1999
Buku Teks