- [S33] Burke's Peerage and Gentry Website, (http://www.burkes-landed-gentry.com;), 107th edition, De Montmorency lineage (Reliability: 2).
- [S205] FreeBMD, (www.freebmd.org.uk;), marriages of Evelyn Henry M P Pearson and Mabel A Throckmorton share reference St. Geo. H. Sq. 1a 811, June quarter 1895 (Reliability: 2).
- [S205] FreeBMD, (www.freebmd.org.uk;), marriage of Willoughby J M (Viscount Frankfort de Montmorency) De Montmorency and Mabel A Pearson, Kensington 1a 341, March quarter 1916 (Reliability: 3).