Claim: Mozart's friendship with Haydn can be seen in the quartets he published in 1785, dedicated to Haydn at a time where most pieces were dedicated to aristocrats.
Evidence: Mozart's six quartets dedicated to Haydn (K. 387, K. 421, K. 428, K. 458, K. 464, and K. 465) date from the period 1782 to 1785, and are judged to be a response to Haydn's Opus 33 set from 1781. Mozart met Joseph Haydn in Vienna around 1784, and the two composers became friends.