Entreves, A.P.D
Hutchinson of London, 1970
Buku Teks
Maris, Cees
Springer, 2011
eBooks
Patrick, George Thomas White
George Allen and Unwin, 1925
Buku Teks SO
Brightman, Edgar Sheffield
Holt, Rinehart and Winston, 1961
Buku Teks SO
Randall, John Herman
Barnes & Noble, 1957
Buku Teks SO