Pontryagin cohomology operation

In mathematics, a Pontryagin cohomology operation is a cohomology operation taking cohomology classes in "H"2"n"("X",Z/"p""r"Z) to "H"2"pn"("X",Z/"p""r"+1Z) for some prime number "p". When "p"=2 these operations were introduced by and were named Pontrjagin squares by (with the term "Pontryagin square" also being used). They were generalized to arbitrary primes by .