United Kingdom of Great Britain and Ireland
Robert Herdman by William Brodie, SNPG.jpg
Robert Herdman (1860s), by Nesbitt & Lothian.jpg
Dictionary of National Biography, 1885–1900
Robert Herdman's grave, Grange Cemetery, Edinburgh.jpg
WikiProject PCC Wikidata Pilot/Frick Art Reference Library
Smithsonian American Art and Portrait Gallery Library