  We show that the continuum hypothesis implies there exists a Lindelof space X
such that X x X is the union of two metrizable subspaces but X is not
metrizable. This gives a consistent solution to a problem of Balogh, Gruenhage,
and Tkachuk. The main lemma is that assuming the continuum hypothesis there
exist disjoint sets of reals X and Y such that X is Borel concentrated on Y,
(i.e., for any Borel set B if Y is contained in B then X-B is countable,) but
(X x X - diagonal) is relatively Fsigma in (X x X) U (Y x Y).
