^An editorial notice in the April 1938 issue made it clear Campbell was responsible for stories appearing as early as February. The editorial note was not signed, but it refers to stories bought for the last three issues, one of which (Lester del Rey's "The Faithful") is known to have been bought by Campbell.
^For example, The Encyclopedia of Science Fiction says "The beginning of Campbell's particular Golden Age of SF can be pinpointed as the summer of 1939," and goes on to begin the discussion with the July 1939 issue. Lester del Rey comments that "July was the turning point."
^Science-fiction writer and critic Damon Knight commented in his book In Search of Wonder: "In the pantheon of magazine science fiction there is no more complex and puzzling figure than that of John Campbell, and certainly none odder." Knight also wrote a four-stanza ditty about some of Campbell's new interests. The first stanza reads:
Oh, the Dean Machine, the Dean Machine,
You put it right in a submarine,
And it flies so high that it cannot be seen –
The wonderful, wonderful Dean Machine!
^In 1957, novelist and critic James Blish tallied: "From the professional writer's point of view, the primary interest in Astounding Science Fiction continues to center on the editor's preoccupation with extrasensory powers and perceptions ('psi') as a springboard for stories ... 113 pages of the total editorial content of the January and February 1957 issues of this magazine are devoted to psi, and 172 to non-psi material ... By including the first part of a serial that later becomes a novel about psi the total for these first two issues of 1957 is 145 pages of psi text, and 140 pages of non-psi."