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