Cowles, 1996
Buku Referensi
Babbitt, Harold E. (Harold Eaton), 1888-, author
McGraw-Hill, 1960
Buku Teks
Church, James C., author
McGraw-Hill, 1979
Buku Referensi
Woodson, R. Dodge, author
McGraw-Hill, 1994
Buku Referensi
Townsend, A. L., author
IKIP Semarang Press , 1986
Buku Teks