LEB writes seminal article offering critical origin analysis of priesthood/temple restriction.
Lester E. Bush, Jr. "Mormonism's Negro Doctrine: An Historical Overview," Dialogue: A Journal of Mormon Thought 8, Spring 1973, 49
For the faithful Mormon a fourth question, less amenable to research, also poses itself: Have our modern prophets received an unequivocal verification of the divine by origin of the priesthood policy, regardless of history? The lack of a tangible answer to the fourth question emphasizes even more the need for greater insight into the first three. We have the tools and would seem to have the historical resource material available to provide valid answers to these questions. Perhaps it's time we began.