A more sober analysis of these claims was published by Gregory McIntosh, a historian of cartography, who examined the map in depth in his book "The Piri Reis Map of 1513" (Athens and London: University of Georgia Press, 2000). He was able to find sources for much of the map in Columbus's writings. Certain peculiarities (such as the appearance of the Virgin Islands in two locations) he attributed to the use of multiple maps as sources; others (such as the errors in North American geography) he traced to the continued confusion of the area with East Asia. As far as the accuracy of depiction of the supposed Antarctic coast is concerned, there are two conspicuous errors. First, it is shown hundreds of kilometres north of its proper location; second, the Drake Passage is completely missing, with the Antarctic Peninsula presumably conflated with the Western Patagonian coast. The identification of this area of the map with the frigid Antarctic coast is also difficult to reconcile with the notes on the map which describe the region as having a warm climate.