Petrocelly, K.L., author
Fairmont Press, Inc., 1993
Buku Referensi
edited by George R. Davis
McGraw-Hill, 1982
Buku Teks
Lawrece, D.H.
Williams Heinemann, 1934
Buku Teks
Cha, Dong Yeop, author
Dong-I, 2007
Buku Teks
Steinhaus, A., author
Mir, 1966
Buku Teks