Complex sentence: He received grants from Guggenheim Fellowship in 1967, Ford Foundation in 1968, and the American Academy in 1970, which allowed him to write a political non-fiction book, opening new doors of opportunity.
Split into simpler sentences: He received grants from Guggenheim Fellowship in 1967, Ford Foundation in 1968, and the American Academy in 1970. The grants allowed him to write a political non-fiction book that opened new doors of opportunity.