 In 1911 Hermann von Rohden and Hermann Winnefeld published "Architektonische Römische Tonreliefs der Kaiserzeit" ("Roman Architectural Clay Reliefs of the Imperial Period") with a volume of images in Reinhard Kekulé von Stradonitz's series "Die antiken Terrakotten".This was the first attempt to organise and classify the reliefs according to the emerging principles of Art history.The two authors first distinguished the main types, discussed their use and considered their development, style, and iconography.