Norton, Alan
Cheltenham Edward Elgar, 1997
Buku Teks SO
edited by Herbert L. Marx
H.W. Wilson, 1962
Buku Teks
Fisher, Ronald C.
Routledge, 2016
Buku Teks SO
Fisher, Ronald C.
Routledge, 2022
eBooks
Fisher, Ronald C.
Scott, Foresman, 1988
Buku Teks SO