Classic X-Men
The X-Men defeat the X-Sentinels, but the damaged space station forces Jean to pilot the shuttle home despite knowing the radiation will kill her.
Collects Giant-Size X-Men #1, X-Men #94-131
Collects X-Factor #1 and Classic X-Men backup stories. The resurrection of Jean Grey and the founding of X-Factor by the original five X-Men.
Collects X-Factor #1; Classic X-Men #8, #43.
Collects X-Factor #1-9 and material from 4 other series. The original X-Factor earliest issues - the five originals reunite plus Rise of Apocalypse.
Collects X-Factor #1-26, X-Factor Annual #1-2, Classic X-Men #8, 43. The original five X-Men reunite, featuring Angel's transformation into Archangel.
Collects Classic X-Men #1-23. Classic X-Men reprints with new backup stories by Claremont and Bolton expanding the Cockrum/Byrne era.
Collects X-Men #97-138 and Classic X-Men backups. The definitive collection — from the Shi'ar saga through the complete Dark Phoenix Saga with bonus material.