The revision issue has generated controversy. A common explanation for the multiple versions is that Bruckner was willing to revise his work on the basis of harsh, uninformed criticism from his colleagues. "The result of such advice was to awaken immediately all the insecurity in the non-musical part of Bruckner's personality," musicologist Deryck Cooke writes. "Lacking all self-assurance in such matters, he felt obliged to bow to the opinions of his friends, 'the experts,' to permit ... revisions and even to help make them in some cases." This explanation was widely accepted when it was championed by Bruckner scholar Robert Haas, who was the chief editor of the first critical editions of Bruckner's works published by the International Bruckner Society; it continues to be found in the majority of program notes and biographical sketches concerning Bruckner. Haas's work was endorsed by the Nazis and so fell out of favour after the war as the Allies enforced denazification.