Ely, Richard T.
University of Wisconsin Press, 1964
Buku Teks
Ratcliff, Richard U.
McGraw-Hill, 1949
Buku Teks
edited by W.L. Gibson, Jr, R.J. Hildreth, Gene Wunderlich
University of Nebraska Press, 1966
Buku Teks
Ely, Richard T.
Macmillan, 1924
Buku Teks
Barlowe, Raleigh
Prentice-Hall, 1958
Buku Teks