Drewe, Robert, author
Council of Adult Education, 1997
Buku Teks
Branner, Robert
George Braziller, 1961
Buku Teks
Harris, robert, author
Arrow Books, 2012
Buku Teks
Ross, Robert, author
N.Y. Barnes & Noble Books, 1974
Buku Teks
Crouch, Robert L.
Harcourt Brace Jovanovich , 1972
Buku Teks