Cambridge University Press, 2009
eBooks
Open University Press,, 2003
Buku Teks
Warner, Jill Diana, author
Elsevier , 2005
Buku Teks
Williangton, C. Oliver
D. Van Nostrand Co., 1956
Buku Teks
Wellington, C. Oliver
van Nostrand, Comp., Inc , 1960
Buku Teks