Artikel Jurnal
edited by Rosemary Clark, D.W. Livingstone, and Harry Smaller
Sense, 2012
eBooks
Zand, Dale E., author
McGraw-Hill, 1981
Buku Teks
editors, Marshall Goldsmith, Howard Morgan, Alexander J. Ogg
John Wiley & Sons, 2004
Buku Teks
edited by Susan J. Peters
Garland, 1993
Buku Referensi