D.J.Benson and J.F.Carlson
The cohomology of extraspecial groups.
Bull. London Math. Soc. 24 (1992), 209-235.
MR 93b:20087, ZB 795.20038
Correction: Bull. London Math. Soc. 25 (1993), 498.
MR 94f:20099, ZB 801.20026