Larry Lieber per Steve Whitaker and Nick Caputo; original indexer credited Marie Severin. Ed Hannigan is the consensus attribution of The Official Marvel Index to the X-Men (Olshevsky 1987), The Official Marvel Index to the X-Men (Ward 1994), and Official Index to the Marvel Universe (Vandal et al. 2009), although Nick Caputo believes the time frame is off and Hannigan was not yet working at Marvel.
Sources for letters credit are The Official Marvel Index to the X-Men (1994) and Official Index to the Marvel Universe; The Marvel Comics Index (Olshevsky 1981) and The Official Marvel Index to the X-Men (1987) attributed letters to Gaspar Saladino.
from The X-Men (Marvel, 1963 series) #41 (February 1968)
from Amazing Adult Fantasy (Marvel, 1961 series) #11 (April 1962)Set in 2061.
Story has 'originally presented in Amazing Adventures #11'.