Notes:
A character who appears to be Thul-Kar appears in the background of the Phantom Zone on page 17, however this must be some other character since Thul-Kar does not enter the Zone until Krypton's last day (see issue #3).
Notes:
Snyder credit per Gary Usher's Robin Snyder Comic Book List. History of the Phantom Zone. It is said that the Phantom Zone first appeared in Adventure Comics #283 (April 1961).