Ely, Richard T.
University of Wisconsin Press, 1964
Buku Teks SO
Luque, Jaime
Springer International Publishing, 2015
eBooks
Ely, Richard T.
Macmillan, 1924
Buku Teks
Ratcliff, Richard U.
McGraw-Hill, 1949
Buku Teks
Barlowe, Raleigh
Prentice-Hall, 1958
Buku Teks