1George Edward Cokayne, Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Vol. 6 N to R, p. 418 (1895).
"III. 1251. 2. WILLIAM, EARL OF ROSS [S.], s. and h., was, v.p., witness to a charter as "William, s. of Earl Ferquhard.' in Sep. 1232. He obtained the isles od Skye and Lewis from Alexander II. [S.] He m. Jean, da. of William COMYN, by his first wife, which William became, about 1210, in right of his second wife, EARL OF BUCHAN [S.] He d. at Earl's Allan, May 1274.".