Neal Adams joined Roy Thomas on the Avengers with issue #93 (1971) to kick off the Kree-Skrull War. That story was titled This Beachhead Earth by Thomas.
Adams originally wanted the story to be titled Three Cows Shot Me Down! As you all know, the story opens with the Vision stumbling into Avengers Mansion. He's severely damaged after a skirmish with three cows...who happen to be Skrulls in disguise! When the Kree-Skrull saga was collected in trade paperback, Adams was able to use his original title on this dynamic new cover.
Here are the pencils to this cover. This was published in the Neal Adams 2007 sketchbook. Adams commented: You have no idea how many years I have waited to put those words on this picture.
And now the inked version, which was featured in the Neal Adams 2008 sketchbook.
For more tidbits on Neal Adams Avengers (and other Marvel) work, you can read the excellent interview with him from TwoMorrows Comic Book Artist #3. Nuff said.