The Animated Series (TAS)
As postulated by Gene Roddenberry, The Animated Series did not belong to Star Trek's canon and was therefore missing in official reference works. In accordance to this previous decision, I did not take into account events from TAS on this website. On the other hand, as opposed to the bulk of non-canon novels or fan work, the series was produced by Roddenberry himself (supported by many of the TOS staff and most of the original cast's voices), with the clear intention to act as a follow-up to TOS. As such, TAS may at least bear some useful background information, and was included here for the sake of completeness, even before it was arbitrarily declared canon.
The Problems of Canonizing TAS - dealing with possible continuity and compatibility issues