Complex sentence: In full, Verdi supplied the anecdotes of how this came about in his 1879 "Sketch", but before that happened, Verdi returned to Busseto for two-and-a-half years.
Split into simpler sentences: In full, in his 1879 "Sketch", Verdi supplied the anecdotes of how this came about. However, before that happened, Verdi returned to Busseto for two-and-a-half years.