Holmes, Vicki L., author
Cambridge University Press, 2001
Buku Teks
Drake, Barbara, author
Harcourt Brace College, 1994
Buku Teks
Flesch, Rudolf
Harper & Row Publishers, 1962
Buku Teks
Kennedy, X. J., author
Pearson, 2016
Buku Teks
Lauchman, Richard, author
American Management Association;;, 1993
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