^Hayes, Dean (2006). The Who's Who of Cardiff City. Derby: Breedon Books. pp. 145–146. ISBN1-85983-462-0.
^Harry O'Neill at the English National Football Archive (subscription required)
^"Football's advent. The Wednesday". Athletic News. Manchester. 15 August 1921. p. 6.
^"Harry O'Neill". adrianbullock.com. Retrieved 19 November 2018.
^"Harry O'Neill". swindon-town-fc.co.uk. Retrieved 19 November 2018.
This biographical article related to association football in England, about a defender born in the 1890s, is a stub. You can help Wikipedia by expanding it.