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@JDHamkins @AndresECaicedo1 Yes, in the Beitrage he goes forth only and proves upon completion that the map is surjective. See "Who put the back in back-and-forth": https://t.co/csYhoF4FFG
@JDHamkins @AndresECaicedo1 Yes, in the Beitrage he goes forth only and proves upon completion that the map is surjective. See "Who put the back in back-and-forth": https://t.co/csYhoF4FFG