Little, Ian M.D.
Clarendon, 1953
Buku Teks
Walker, Clive
Manchester University Press, 1986
Buku Teks
Day, A.C.L.
Clerendon Press, 1967
Buku Teks
Carter, C.F.
Oxford University Press, 1958
Buku Teks SO
Backman, Jules
Brookings Institution, 1943
Buku Teks