Donzelli, Aurora
2003
Artikel Jurnal
Tibbetts, A.M.
Scott, Foresman and Company, 1979
Buku Teks
Connolly, Francis
Harcourt, Brace & World, 1969
Buku Teks
Heery, Mike
Aslib, 1996
Buku Teks
Hose, Charles, 1863-1929
Oxford University Press, 1993
Buku Teks