Woulfe, Patrick (1923): «Ó Fearghail». Irish Names and Surnames. Dublin: M.H. Gill. Sitat: «The head of the family resided at the town of Longford, which was formerly known as Longphort Ui Fhearghail, or O'Farrell's fortress.»
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Gearty, Sarah; Morris, Martin; O'Ferrall, Fergus (2010): «No. 22 - Longford» (PDF). Irish Historic Towns Atlas. Royal Irish Academy. Sitat: «Longford stands on a fording point of the Camlin River though the town's name does not derive from its position on a ford, but comes from the Irish Longphort, meaning fortress or stronghold.»
