During the early 1920s he published six major works in the areas of government, public law, and international law: in 1920, "Das Problem der Souveränität und die Theorie des Völkerrechts" (The Problem of Sovereignty and Theory of International Law) and "Vom Wesen und Wert der Demokratie" (On the Essence and Value of Democracy); in 1922, "Der soziologische und der juristische Staatsbegriff" (The Sociological and Juristic Concepts of the State); in 1923, "Österreichisches Staatsrecht" (Austrian Public Law); and, in 1925, "Allgemeine Staatslehre" (General Theory of the State), together with "Das Problem des Parlamentarismus" (The Problem of Parliamentarianism). In the late 1920s, these were followed by "Die philosophischen Grundlagen der Naturrechtslehre und des Rechtspositivismus" (The Philosophical Foundations of the Doctrine of Natural Law and Legal Positivism).