Mahmoud, Shah
Betterway, 1992
Buku Referensi
Atwan, Robert
McGraw-Hill, 1987
Buku Teks
Lester, James D.
Scott, Foresman and Company, 1987
Buku Teks
Lester, James D.
Scott, Foresman and Company, 1971
Buku Teks
Laster, James D
Scott, Foresman and Company, 1984
Buku Teks