A long time has passed since this thread was started, but nevertheless: where (as in bibliographical reference) can one find the result of Quillen which you mention at 1)?

@DanieleTampieri You are most kind to have taken the time to find a solution to this matter! I will try to see if the Atti can be found somewhere locally near me, and if not I will get in touch with you at the email address you have specified. With regards〜

@DanieleTampieri I would like to ask you one more question: how can one gain access to the Atti dei Convegni Lincei? They do not seem to be available online, but I would be interested in obtaining a copy of the article you recommended. With regards〜

@nombre Thank you for the detailed aswer!

@DanieleTampieri Thank you kindly for your suggestion!