Archer, James. "Trade Union membership 2010"(PDF). Department for Business Innovation and Skills. Archived(PDF) from the original on 1 November 2013. Retrieved 23 August 2013.
Archer, James. "Trade Union membership 2010"(PDF). Department for Business Innovation and Skills. Archived(PDF) from the original on 1 November 2013. Retrieved 23 August 2013.