Justice League of America #30

THE MOST DANGEROUS EARTH OF ALL Just as the super-heroes of the Justice League Of America exist on Earth-One -- and as the super-heroic Justice Society Of America lives on Earth-Two -- there is a super-villainous Crime Syndicate Earth Three!  These super-villains, who dominate their earth because they are the only super-beings on it, find their fighting edge dulled from lack of effective competition. When Ultraman develops a new power by exposure to on green kryptonite, he discovers Earth-One and the Justice League. Entering Earth-One, the Crime Syndicate does battle with the Justice League and is on the verge of defeat when -- thanks to the trickiness of Owlman -- the villains save themselves by vibrating with their foes into Earth-Three where they gain a victory on their home grounds!  Seeking a neutral battleground for a showdown battle with the Justice League, the Crime Syndicate finds Earth-Two. To insure complete neutrality, they decide to oust the Justice Society from their own world. Detecting Ultraman's vision peering into their Earth, the Justice Society, through the magic of Doctor Fate, contacts the Justice League and discovers what has occurred so far!