Tischler, Henry L.
Wadsworth and Cengage Learning, 2014
Buku Teks
Brinkerhoff, David B., author
Wadsworth, Cengage Learning, 2014
Buku Teks
Mckee, James B., author
Holt, Rinehart and Winston, 1969
Buku Teks
Barnes & Noble Books, 1969
Buku Teks
R. Vassilev
Publishing House of the Bulgaria, 1970
Buku Teks