Schonemann's criterion

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For a polynomial q denote by $q^*$ the residue of $q$ modulo $p$. Suppose the following conditions hold: <list> <it> $k=f^n+pg$ with $n\geq 1$, $p$ prime, and $f,g\in \mathbb{Z}[X]$. <it> $\text{deg}(f^n)>\text{deg}(g)$ <it> $k$ is primitive <it> $f^*$ is irreducible in $\mathbb{F}_p[X]$. <it> $f^*$ does not divide $g^*$. <\list> Then $k$ is irreducible in $\mathbb{Q}[X]$.

See also Eisenstein's criterion.