Young, Jay A.
Macmillan, 1978
Buku Teks
Sackheim, George I.
Macmillan, 1973
Buku Teks
Suckling, Colin J.
Universal Book Stall, 1995
Buku Teks
Seager, Spencer L., author
Scott, Forestman and Company, 1973
Buku Teks
Stark, Edward C., author
Glencoe, 1979
Buku Teks