 Going-up theorem

For an integral extension $A\subseteq B$, primes ${\mathfrak{p}}_1\subseteq {\mathfrak{p}}_2$ of $A$, and a prime ${\mathfrak{q}}_1$ of $B$ over ${\mathfrak{p}}_1$, there is a prime ${\mathfrak{q}}_2\supseteq {\mathfrak{q}}_1$ over ${\mathfrak{p}}_2$.