[Photograph of a painting by Housman.]
Gudeman's portrait was of Izaak Walton by Jacob Huysmans.
This
engraving of Grotius appeared in Johann Nicolas Serlin's (ed.)
Hugonis Grotii Drey Bücher von Kriegs- und Friedens-Rechten (Frankfurt 1709) and was uploaded to Wikimedia Commons on 23 May 2014.