For a path-connected, locally path-connected, and semilocally simply-connected space X, call a path-connected covering space X~→X abelian if it is normal and has abelian deck transformation group. Show that X has an abelian covering space that is a covering space of every other abelian covering space of X, and that such a 'universal' abelian covering space is unique up to isomorphism. Describe this covering space explicitly for X=S1∨S1 and X=S1∨S1∨S1.