The principle of legitimacy in state practice since the Vienna Congress is a scholarly book that deals with the development and application of the principle of legitimacy in international politics since the Vienna Congress of 1815. Written by Alexander Gauland, the work offers an in-depth analysis of the political and legal frameworks that shape state practice. The paperback cover and the German language make the book an accessible resource for students and professionals in the fields of economics and law. With 110 pages, it provides a compact yet comprehensive presentation of the topic, considering both historical and contemporary perspectives. The book was published in 1972 and falls into the category of non-fiction that addresses mathematics and natural sciences. It is a valuable reference work for anyone interested in the foundations of international relations and the legitimacy of states.