United Kingdom of Great Britain and Ireland
Richard Redgrave - Self-portrait (ca. 1832) - Google Art Project.jpg
Dictionary of National Biography, 1885–1900
Brockhaus and Efron Encyclopedic Dictionary
Paintings of the nineteenth century: contribution to the history of art
WikiProject PCC Wikidata Pilot/Frick Art Reference Library
Smithsonian American Art and Portrait Gallery Library
Mapping the Practice and Profession of Sculpture in Britain and Ireland 1851–1951