Hale, Tammy J.
Delmar, 2011
Buku Teks SO
Billings, Diane M.
Elsevier/Saunders, 2012
Buku Teks SO
Knowles, Malcolm S.
Association Press, 1976
Buku Teks
Robinson, Kate
Open University Press, 1995
Buku Teks SO
Dolphin, Patricia
Reston Publishing, 1983
Buku Teks SO