"Flash of Two Worlds!" is a landmark comic book story that was published in The Flash #123. It introduces Earth-Two, and more generally the concept of the multiverse, to DC Comics. The story was written by Gardner Fox under the editorial guidance... Wikipedia
Originally published: September 1961
Author: Gardner Fox
Inker(s): Joe Giella
Main character(s): Flash (Barry Allen); Flash (Jay Garrick)
Title(s): The Flash #123