Korean Overseas Information Service, 1993
Buku Referensi
Sprague, Jo, author
Wadsworth/Cengage Learning, 2013
Buku Teks
Dietsch, Betty Mattix, author
McGraw-Hill, 2003
Buku Teks
Gerson, Sharon J., 1948-, author
Prentice-Hall, 1992
Buku Teks
Kim, Se-Kwon, author
Wiely-Blackwell, 2012
Buku Teks