THAT VIKINGS crossed the Atlantic long before Christopher Columbus is well established. Their sagas told of expeditions to the coast of today’s Canada: to Helluland, which scholars have identified as Baffin Island or Labrador; Markland (Labrador or Newfoundland) and Vinland (Newfoundland or a territory farther south). In 1960 the remains of Norse buildings were found on Newfoundland.But there was no evidence to prove that anyone outside northern Europe had heard of America until Columbus’s voyage in 1492. Until now. A paper for the academic journal Terrae Incognitae by Paolo Chiesa, a professor of Medieval Latin Literature at Milan University, reveals...