On-sale date from copyright registration.
Story in two parts of 8.67 pages and 5.67 pages.
Writing credit provided by Bob Hughes.
Between pages 9-10 of main story sequence.
Page includes the information that Green Lantern #21 was written by John Broome, and illustrated by Gil Kane and Joe Giella.
A letter from Phil Cetrone notes that the story "The Man Who Mastered Magnetism" in Green Lantern 21, was drawn by Gil Kane, and inked by Joe Giella: the editor does not refute this. A letter from Bob Beck notes that the same story was written by John Broome: the editor does not refute this either. Another letter from Jack Harris notes that he sent in the idea for the cover of that same issue, and the editor states that for providing the idea, he sent Mr. Harris the original art for the cover.
The planet "Green Lantern" has NO Green Lantern powers, it takes the name in honor of Hal Jordan. The "imitation" characters are constructed by the planet.
Bob Rozakis, in Green Lantern #100 (January 1978), credited Joe Giella (and not Frank Giacoia) with this story’s inks. In Green Lantern Annual #1 (1998), Giacoia and Giella were both credited with inks. The Giacoia and Giella credits were repeated in Showcase Presents Green Lantern #2 (2007).