C. Pinkerton / G. McLaughlan / J. Salt, Sizing the illegally resident population in the UK, in: Home Office Online Report 58/2004, p. 1 ([Internet, 2025-12-08](https://www.ons.gov.uk/file?uri=/aboutus/transparencyandgovernance/freedomofinformationfoi/illegalimmigrantsintheuk/sizing_illegal_pop.pdf))