Sue: no guarantee, but 80% of gross receipts over estimated expenses of $5,105, plus 80% of difference between estimated and actual expenses.
ad: San Francisco Sunday Examiner and Chronicle Datebook, July 12, 1981, p. 9
ad: BAM, July 31, 1981, p. 4
preview: "Garcia Band to play in Stockton," Lodi News-Sentinel, August 6, 1981, p. 10, accessed via Google News; this preview names the personnel, less the singers: Jerry Garcia, John Kahn, Melvin Seals, Daoud Shaw on drums, and Jimmy Warren on piano, one of the few times you'll see the latter two guys' names in print in the Garciaverse.