United States. Central Intelligence Agency, CIA World Fact Book, 2004 — United Kingdom (2004)
“ England has existed as a unified entity since the 10th century; the union between England and Wales, begun in 1284 with the Statute of Rhuddlan, was not formalized until 1536 with an Act of Union; in another Act of Union in 1707, England and Scotland agreed to permanently join as Great Britain; the legislative union of Great Britain and Ireland was implemented in 1801, with the adoption of the name the United Kingdom of Great Britain and Ireland; the Anglo-Irish treaty of 1921 formalized a partition of Ireland ”
