Loughary, John W., author
Harper & Row, 1966
Buku Teks
Solomon, Cynthia, author
MIT Press, 1986
Buku Teks
Päivi Tynjälä, Marja-Leena Stenström, Marjatta Saarnivaara, editors
Springer, 2012
eBooks
Knowles, Malcolm S., author
Cambridge University Press, 1980
Buku Teks
Arbab, Farzam
International Development Research Centre , 1984
Buku Teks