Church, Horace K.
McGraw-Hill, 1981
Buku Referensi
Herrick, James A.
Pearson custom, 1998
Buku Teks SO
Cornman, James W.
Macmillan, 1968
Buku Teks SO
Mander, Jerry
Morrow Quill Paperbacks, 1978
Buku Teks SO
Williams, Alexander
Cambridge University Press, 2015
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