Elliott, Philip
Herder and Herder, 1972
Buku Teks
Richards, J.M.
Newton Abbot: Davis and Charles, 1974
Buku Teks
Trzyna, Thomas N.
Wadsworth, 1987
Buku Teks
Sampson, Edward E.
John Wiley & Sons, 1981
Buku Teks
Jensen, J. Trygve
John Wiley & Sons, 1982
Buku Teks