1927-10-03: Celtic 4-1 Cardiff City, Friendly – The Celtic Wiki

The Celtic Football Club and the First World War 1914/15

Motherwell 0-4 Celtic: Liel Abada shines as Hoops set up Premier Sports Cup semi-final against Kilmarnock, Football News

Celtic F.C., Football Wiki

The Celtic Wiki – A comprehensive guide to Celtic FC, a football team based in Glasgow, Scotland.

Cardiff City F.C. - Wikipedia

Belfast Celtic – The Celtic Wiki

1962-09-10: Celtic 1-3 Real Madrid, Friendly – The Celtic Wiki

1974-04-10: Celtic 0-0 Athletico Madrid, European Cup – Pictures – The Celtic Wiki

Battle of Britain – The Celtic Wiki

History of Celtic F.C. (1887–1994) - Wikipedia

Celtic Team Line-Up 1958-59 – The Celtic Wiki

2010-03-24: St Mirren 4-0 Celtic, SPL – The Celtic Wiki