Pollock, George
Springer, 2012
eBooks
Hawker, Jeremy
Wiley-Blackwell, 2012
Buku Teks
Ezekiel Kalipeni, Juliet Iwelunmor, Diana Grigsby-Toussaint, Imelda Moise, editors
Routledge, Taylor & Francis Group, 2018
Buku Teks
Nelson, Kenrad E.
Jones & Bartlett Learning, 2014
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Webber, Roger
Cab International, 1996
Buku Teks