Acknowledgements: Antiq-Photo, Dominic Winter Book Auctions, George Eastman Museum, Guildhall Library, Larry Gottheim - Be-hold - Inc, Lee Gallery, Minneapolis Institute of Art - MIA, National Gallery of Australia (NGA), National Gallery of Canada / Musée des beaux-arts du Canada, National Library of Scotland, Paul Frecker, Pierre Spake Fine Art, Private collection of Peter Spangenberg. |