Duality Law for Stirling Numbers

Theorem
For all integers $n, m \in \Z$:


 * $\ds {n \brace m} = {-m \brack -n}$

where:
 * $\ds {n \brace m}$ denotes a Stirling number of the second kind
 * $\ds {n \brack m}$ denotes an unsigned Stirling number of the first kind.