Coba jelasin Silsilah dari Isabella MacDuff dong

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.