Freiman’s theorem

Let $A$ be a finite set of integers such that the $2$-fold sumset $2A$ is “small”, i.e., for some constant $c$. There exists an $n$-dimensional arithmetic progression (http://planetmath.org/MulidimensionalArithmeticProgression) of length $c^{\prime }|A|$ that contains $A$, and such that $c^{\prime }$ and $n$ are functions of $c$ only.