Ravetz, Alison
Croom Helm , 1980
Buku Teks
edited by Peter Roberts and Hugh Sykes
Sage, 2003
Buku Referensi
edited by Peter Roberts, Hugh Sykes
Sage Publications, 2003
Buku Referensi
Choldin, Harvey M.
McGraw-Hill, 1985
Buku Teks
McGraw-Hill, 2000
Buku Teks