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May 28, 2022 at 16:09 history edited Martin Sleziak CC BY-SA 4.0
http -> https (the question was bumped anyway)
Oct 28, 2010 at 2:49 comment added user6976 Ol'shanskii did not rediscover van Kampen diagrams independently of Lyndon. The book of Lyndon and Schupp appeared first and was widely known. However, there were errors in L-S including the proof of the van Kampen lemma (about the diagrams), so many leading group theorists rejected the method in the 60-80s. Ol'shanskii did make everything completely rigorous in his book and earlier papers.
Feb 3, 2010 at 14:02 comment added Steve Huntsman I would say these were "ignored" rather than "rejected".
Feb 3, 2010 at 13:57 history answered Johannes Hahn CC BY-SA 2.5