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The Observer
Complete archive of the Observer newspaper (London, England), including all issues from 1791 to 2003. 

Oxford Dictionary of National Biography (Oxford DNB)
Reference source on key figures in British history and society from 100BC to the present day.  Includes 60,000+ biographies, 11,000+ portraits, plus archival references and bibliographies.

Oxford English Dictionary (OED)
Definitive reference source on the English language, providing a guide to the spelling, meaning, history (etymology), and pronunciation of 600,000+ words across the English-speaking world, using the International Phonetic Alphabet.