Polish Painting Masterpieces
Artur Grottger
"Portrait of Unknown Man", 1860, oil on cardboard, 31.5 x 23 cm, National Museum, Wroclaw

Source: „Artur Grottger, 1837-1867”, „Wielka kolekcja slawnych malarzy” series, Oxford Educational, Poznan 2008, ISBN 978-83-252-0123-4