A correction, a retraction, and addenda to my paper ''Another example of a finitely presented infinite simple group'' (Q790936)

The author retracts the claim made in his earlier paper that the (infinite, finitely presented) commutator subgroup of a certain group A, is simple. He proves two transitivity results about subgroups of the automorphism group of certain trees, and deduces, via a result of P. Stebe on the residual finiteness of certain amalgamated products, that far from being infinite simple A' is in fact residually finite (as is A). A corrected proof of Lemma 4 (stating that A acts \(\omega\)-transitively on the infinite tree having each vertex incident with 8 edges) is also given. [See Zbl 0469.20018 for the review of the earlier paper (ibid. 69, 261-269 (1981)).]