Standard components of alternating type centralized by a 4-group

We determine the finite groups possessing a standard subgroup which is the covering group of an alternating group, and whose centralizer is of 2-rank at least 2. The result is one step in the original proof of the classification of the finite simple groups, and presumably also in improvements to that proof. The paper is a modification of the original preprint, which had remained unpublished since the seventies.