Title: The Rees algebra of a two-Borel ideal is Koszul,
Abstract: Let $M$ and $N$ be two monomials of the same degree, and let $I$ be the
smallest Borel ideal containing $M$ and $N$. We show that the toric ring of $I$
is Koszul by constructing a quadratic Gröbner basis for the associated toric
ideal. Our proofs use the construction of graphs corresponding to fibers of the
toric map. As a consequence, we conclude that the Rees algebra is also Koszul.