16 sources
Adventure Comics (vol. 1) #371 (Aug. 1968): "The Colossal Failure!"Captain America (vol. 1) #104 (Aug. 1968): "Slave of the Skull!"Captain Marvel (vol. 1) #4 (Aug. 1968): "The Alien and the Amphibian!"Captain Savage #5 (Aug. 1968): "Mission: Destroy the Invisible Enemy"Daredevil (vol. 1) #43 (Aug. 1968): "In Combat with Captain America!"Doctor Strange (vol. 1) #171 (Aug. 1968): "In the Shadow of... Death!"Hang 'Em High (1968)Justice League of America (vol. 1) #64 (Aug. 1968): "The Stormy Return of the Red Tornado!"Nick Fury, Agent of S.H.I.E.L.D. (vol. 1) #3 (Aug. 1968): "Dark Moon Rise, Hell Hound Kill!"Sgt. Fury and His Howling Commandos (vol. 1) #57 (Aug. 1968): "The Informer"Showcase #76 (Aug. 1968): "Pheasant in Aspic"The Silver Surfer (vol. 1) #1 (Aug. 1968): "The Origin of the Silver Surfer"The Sub-Mariner (vol. 1) #4 (Aug. 1968): "Who Strikes for Atlantis?"Thor (vol. 1) #155 (Aug. 1968): "Now Ends the Universe!"
The X-Men