Ohio North Light Books, 1992
Buku Teks SO
arranged and edited by Wolfgang Hageney
Belvedere, 1989
Buku Teks SO
Harper, Laurel
Chronicle Books, 1999
Buku Referensi
Geary, David M.
Prentice-Hall, 1997
Buku Teks SO
Ramsey
John Wiley & Sons, 1994
Buku Referensi