Complex sentence: The group was the creation of John Irving in his novel "The World According to Garp", from which, in 1982, was made a movie adaptation starring Robin Williams and Glenn Close at her first feature, with a screenplay written by Steve Tesich.
Split into simpler sentences: The group was the creation of John Irving in his novel "The World According to Garp". A movie adaptation of the novel starring Robin Williams was released in 1982, with a screenplay written by Steve Tesich.