Batschelet, Edward
Springer-Verlag , 1975
Buku Teks
Gill, Philip E.
Academic Press , 1981
Buku Teks
Smith, Peter F., author
Routledge, 2003
Buku Teks
Kaligis, O.C. (Otto Cornelis), 1942-, author
Alumni, 2010
Buku Teks
Feuer, Alan R., author
Prentice-Hall, 1982
Buku Teks