The Vinland Map and the Tartar Relation, by R. A. Skelton (oversize HC, 1965, $5)
"This book contains two documents copied about 1440 from much earlier originals, now lost. The first is an account of Friar John of Plano Carpini's mission to the Mongols in 1245-47. The second is a world map, including the western ocean, with delineations of Iceland, Greenland, and a land mass named Vinland which represents the North American mainland as know to the medieval Norsemen."
"A first-rate bibliohistorical detective story of major importance."
Look for this book in western civ., for lack of a better place to put it into.