That Half-Barbaric Twang: THE BANJO IN AMERICAN POPULAR CULTURE 

http://books.google.com/books?id=ra35uzp5gJQC&printsec=frontcover#v=onepage&q&f=false

African Banjo Echoes In Appalachia: Study Folk Traditions

http://www.betterworldbooks.com/african-banjo-echoes-in-appalachia-study-folk-traditions-id-9780870498930.aspx

https://books.google.com/books?id=2xfOMgDFHNwC&pg=PA51&lpg=PA51&dq=rex+professional+banjo&source=bl&ots=ksPchGPIJD&sig=N78-9cfXzFwe1xMqBNZMwSk2TxQ&hl=en&sa=X&ei=nO7pVMSaJMX_gwTRjoNI&ved=0CFEQ6AEwCQ#v=onepage&q=rex%20professional%20banjo&f=false