 In large measure these were a result of the 1819 Carlsbad Decrees which, "inter alia", expanded the censorship of the press.Censorship was enforced through the requirement to have a government license to publish books or newspapers, and the mandatory use of an impressum on printed material to identify authors and publishers.However, the city-republics such as Frankfurt and Hamburg tended to have a free press, a rarity in 19th century Germany.