Notes
Later editions of "Destination Void" mention being based on a story "Do I Sleep or Wake" in Galaxy around this time. That probably is a variant of this title or one of the publications is erroneous.
The 12th Berkley printing of "The Eyes of Heisenberg" also claims to be based on a story "Do I Sleep or Wake" in Galaxy in 1965. AS that credit is obviously wrong (Since Heisenberg itself was serialized in Galaxy) there appears to have been a 'rash' of incorrect attributions of 'based on' to the never published variant title "Do I Sleep or Wake".