Ivamy, E.R. Hardy
Butterworths Insurance Library, 1985
Buku Teks
Guerard, Albert J.
Harvard University Press, 1949
Buku Teks
Hardy, W.G.
Schenkman Publishing Company Inc., 1962.
Buku Teks
Universitas Indonesia, 2008
UI - Skripsi (Membership)
Hardy, Darel W.
Wadsworth , 1975
Buku Teks