Perthel, Dirk, author
Amsterdam University, 1981
Buku Teks
Bjornson, Gordon B.
Vantage Press , 1971
Buku Teks
Massachusetts Addison-Wesley , 1950
Buku Teks
Mishan, E.J.
Penguin Books, 1969
Buku Teks
by H.G. Johnson... [and others]
Macmillan, 1968
Buku Teks