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Iain Grahame Rare Books - Specialist in rare natural history books, shooting books, stalking books, hunting books, fishing books, bird books and africana books and prints.
www.iaingrahamerarebooks.com/

Ice House Books - Second-hand and antiquarian books and publications; special interests include socialist, marxist and progressive fiction and non-fiction in English and other languages.
www.icehousebooks.co.uk/

The Ink Company - Rare and out of print books, sorted by specialty and searchable.
www.inkcobooks.com/

Inlibris - Fine and rare books; specializes in autographs, manuscripts, and archives of significant personalities of science and the arts.
www.rarebooksandautographs.com/

Isis Antiquarian Books - Specialises in Philosophy, with books about art, history, religion and literature. Bilingual English and Dutch.
www.isis-books.nl/english/english.htm