A recent study has concluded that geographical distance has very little, if any, influence upon communities' selections of a twin town. Twinned towns are often chosen because of similarities between them; thus about 15 towns in Wales are twinned with towns in Brittany, and Oxford is with Bonn, Leiden, Grenoble and other university cities. In Italy, two sets of twins are Rovigo with Viernheim, and Bedford with Tulcea. Many former West German cities are twinned with former East German cities; these twinning links were established before the fall of the Iron Curtain. Famous examples are the partnerships of Hanover and Leipzig, both of which have important trade fair grounds, or between Hamburg and Dresden. The first US-German town twinning was in 1947 between Worthington, Minnesota and Crailsheim.