Nelson, Stanley J., author
Elsevier Saunders, 2015
Buku Teks
Geroski, Paul, author
Harwood Academic Publishers , 1990
Buku Teks
Michalsen, Venezia, 1976-, author
Routledge, Taylor & Francis Group, 2019
Buku Teks
University of Leeds, 1994
Buku Referensi
Root, Franklin R., author
Lexington Books, 1987
Buku Teks