In the original series episode, "All Our Yesterdays", Spock goes back in time 4000 years into a particular planet's history.
Two sequels to this episode were written as novels. "Yesterday's Son" and "Time for Yesterday" in which it is revealed, among other things, that:
Spock had a son with that nice cave lady.
I am wondering which episodes of The Next Generation have similar sequels or prequels, and is there a comprehensive list of such things, perhaps including all the series?