Robert Ferguson, The Vikings: A History, New York: Viking, 2009, However, recent archaeological research and the re-evaluation of large pits on the west side of the north mound which were noted in the 1960s has led to a different reconstruction, in which the ship had the north mound as its centre rather than its stern and was 354 meters long; this length corresponds to 1,200 Roman feet, and the Trelleborg fortresses were also measured out in Roman feet.