Coimbra Group, 1994
Buku Referensi
Mountford, James, Sir, author
Oxford Unniversity Press, 1966
Buku Teks
Mordechai Feingold, editor
Oxford University Press, 2016
eBooks
MacTaggart, Terrence J.
Jossey-Bass , 19989
Buku Teks
Magabook, 1994
Buku Referensi