Does anybody know where I might find a proof for the Frank-Wolfe Theorem (stated below)?
Frank-Wolfe Theorem: If a quadratic function $f$ is bounded below on a nonempty polyhedron (the intersection of finitely many half-spaces) $X$, then there exists $\bar{x} \in X$ such that $f(\bar{x}) \leq f(x)$ for all $x \in X$, i.e. $f$ attains its infimum on $X$.