Martin Schlag, Juan Andres Mercado, editors
[Springer, Springer], 2012
eBooks
Nadiesyah Hosen, Richard Mohr, editor
Routledge, 2011
Buku Teks
Fedrizzi, Mariann
South Western Cengage Learning, 2011
Buku Teks
Davis, Con
Longman, 1991
Buku Teks
Goodall, Peter
Sr. Leonards Allen & Unwin 1995,
Buku Teks