Tolong jelaskan mengenai Silsilah dari Isabella MacDuff

Grant, Rev'd Alexander, "The Ancient Earls of Fife", in Sir James Balfour Paul (ed.) The Scots Peerage, Volume IV, (Edinburgh, 1907), pp. 13–14

Gray, Thomas, Scalacronica (pub. 1911)

Boardman, Steve, The Early Stewart Kings, Robert II and Robert III (1996), ch. 1, esp. p. 13 ff.