The above bibliography should be updated.

Revised and later discographies are:
Robert M.W. Dixon, John Godrich & Howard W. Rye, eds., Blues and Gospel Records 1890-1943, 4th edition (Oxford, 1997)
Cedric J. Hayes & Robert Laughton, eds., Gospel Records 1943-1969: A Black Music Discography, 2 vols. (Record Information Services, 1993). [Hayes' discography above is far from comprehensive]
Other gospel books include:
Horace Clarence Boyer, How Sweet the Sound: The Golden Age of Gospel (Elliott & Clark, 1995)[republished as The Golden Age of Gospel, by University of Illinois Press; good introduction]
Viv Broughton, Black Gospel: An Illustrated History of the Gospel Sound (Blandford Press, 1985)
Bernice Johnson Reagon, ed., We'll Understand It Better By and By: Pioneering African American Gospel Composers (Smithsonian Institution Press, 1992) [collection of essays, with detailed bibliography]
Michael W. Harris, The Rise of Gospel Blues: The Music of Thomas Andrew Dorsey in the Urban Church (Oxford UP, 1992)

~Masato