Waterson, Roxana
Roxana Waterson, 1997
Buku Referensi
edited by Andrew Blake
Routledge, 1999
Buku Teks
Stanley, Melissa, author
Addison-Wesley, 1984
Buku Teks
edited by David Brower
Sierra Club, 1961
Buku Teks SO
Duffy, Karen G., author
Pearson Education, Inc., 2005
Buku Teks