Locke, Lawrence F., author
Sage, 2000
Buku Teks
Locke, Lawrence F., author
Sage, 1987
Buku Referensi
Locke, Lawrence F., author
Sage, 2014
Buku Teks
Denscombe, Martyn, author
Open University Press, 2012
Buku Teks
Jähne, Johannes, author
Edition Leipzic, 1964
Buku Teks