Isla. In: Francis H. Groome: Ordnance Gazetteer of Scotland: A Survey of Scottish Topography, Statistical, Biographical and Historical. Band 4: (Har – Lib). Thomas C. Jack, Grange Publishing Works, Edinburgh u. a. 1885, S. 326.
scottish-places.info
Isla, River. In: David Munro, Bruce Gittings: Scotland. An Encyclopedia of Places & Landscapes. Collins u. a., Glasgow 2006, ISBN 0-00-472466-6.