most recent 30 from http://mathoverflow.net 2013-06-19T04:23:35Z http://mathoverflow.net/feeds/user/23594 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/96510/have-we-ever-lost-any-mathematics/96553#96553 Per Manne 2012-05-10T08:41:56Z 2012-05-10T08:41:56Z

<p>I was once told of a paper in homological algebra where a new class of functors was introduced, generalizing Ext and Tor. For some years they were studied, and various properties were proved. Finally someone managed to give a complete description of the entire class. It consisted of two elements, Ext and Tor. (Sorry, I don't have more details.)</p>