The legendary folk-rock act Crosby, Stills & Nash will return to the Riverside Theater on Sunday, Aug. 5 as part of their extensive summer tour, the venue announced this morning. For these shows, the trio will be backed by a five-piece band. Reserved-seat tickets are $45 and $65, with a limited amount for V.I.P. seats available for $95. They go on sale Friday, March 23 at noon. <br /><br />Also announced this morning: blues-rock great Bonnie Raitt will perform at the Marcus Center on Wednesday, Aug. 22 at 7:30 p.m. Tickets are $56-$101, and go on sale Friday, March 23 at noon.