Russell Impagliazzo, Pavel Pudlak, Jiri Sgall

Razborov~\cite{Razborov96} recently proved that polynomial

calculus proofs of the pigeonhole principle $PHP_n^m$ must have

degree at least $\ceiling{n/2}+1$ over any field. We present a

simplified proof of the same result. The main

idea of our proof is the same as in the original proof

of Razborov: we want to describe ...
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