Date: Mon, 21 Apr 1997 17:10:03 +0400
From: "Alexei A.Davydov" 
Reply-To: davydov@mech.math.msu.su
Organization: Moscow State UnIversity
 
Dear Forum,
 
It is well known that the second cohomology group H^2(G,A)
classifies extensions of G by A.

When do two elements of H^2(G,A) 
correspond to nonisomorphic groups?
 
Alexei Davydov