Some Notes: 

The Charlatans (October 5-10, 1965):  The Charlatans shows that ran from October 5-10, 1965 may well have had the Jefferson Airplane in support.  If not, at some other time in October 1965, the Charlatans and the Jefferson Airplane did indeed play some shows at the Matrix. 

Final Solution at the Matrix (July 2, 1966): Following some great detective work by Corry Arnold: There is an announcement from the stage where the MC says "We'd like to thank the Final Solution for filling in on such short notice. Tomorrow night the Great Society returns to finish up their engagement. On Tuesday we'll have a great folk-rock group from Berkeley, Country Joe and The Fish, as well as the San Francisco Mime Troupe". The Country Joe/Mime Troupe handbill shows them opening Tuesday, July 5. CJF plays later in July, also, but without the Mime Troupe. I know of no handbill or advertisement for the week before (June 28-July 3) and groups typically played Tuesday through Sunday. The Great Society played the previous week (June 21-26), so it seems they played the week of June 28-July 3 as well, or at least the weekend. I don't know of other Great Society shows during that week. Following the assumption that the Final Solution subbed on Saturday night (as Great Society will "return to finish up" the next night) we note that Great Society played the Fillmore (with The Sopwith Camel and the Charlatans per BG-14) on Saturday July 2. With this in mind, I am dating Final Solution Matrix show as July 2.

Santana (November 13, 1968):  The entry for Santana on November 13, 1968 was taken from the date on a live recording of what is clearly an early show that circulates with both a 1967 and 1968 date.  However, there is no other evidence to substantiate this show took place either at the Matrix or on either of these dates.

Jefferson Airplane (April 13, 1969):  The listing for April 13, 1969 includes the Jefferson Airplane although it is more likely that this was just a Hot Tuna show.

Velvet Underground (December 1-3, 1969): There has always been some question regarding the validity of the Velvet Underground shows at the Matrix on December 1, 1969 through December 3.  Little substantiating evidence had existed that the shows actually took place - aside from the regular inclusion of recordings on tape lists.  Research in to the contemporary press have now identified that Bukka White and Charlie Cockey played the Matrix on those three nights.  As such, the entry has been changed to include White and Cockey as replacing the Velvet Underground.  The evidence of a contemporary newspaper listing for any show is generally more plausible than any posters or handbills that would have been printed weeks before the show.