Morris, Michael A, author
Palgrave Macmillan, 2016
Buku Teks
edited by Malcolm Warner
Business Press, 2000
Buku Referensi
Washington : Pan American Union, General Secretariet of the Organization of American States
Majalah, Jurnal, Buletin
John E. Joseph, author
Edinburgh University Press, 2009
eBooks
Thomson Wadsworth, 2003
Multimedia