Longest, Beaufort B., author
Appleton and Lange, 1996
Buku Teks
Robinson, Alice M., author
Prentice-Hall, 1982
Buku Teks
Longest, Beaufort B., author
Appleton and Lange, 1996
Buku Teks
Northouse, Laurel L., author
Appleton & Lange , 1998
Buku Teks
Northouse, Peter G., author
Prentice-Hall, 1985
Buku Referensi