University of Vienna, where he established and edited the Zeitschrift für öffentliches Recht (Journal of Public Law). At the behest of Chancellor Karl Renner, Kelsen worked on drafting a new Austrian Constitution, enacted in 1920. The document still forms the basis of Austrian constitutional law. Kelsen was appointed to the Constitutional Court, for his lifetime. Kelsen's emphasis during these years upon a Continental form of legal positivism began to further flourish from the standpoint of his law-state monism, somewhat based upon the previous examples of Continental legal positivism found in such scholars of law-state dualism such as Paul Laband (1838–1918) and Carl Friedrich von Gerber (1823–1891). 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). During the 1920s, Kelsen continued to promote his celebrated theory of the identity of law and state which made his efforts a counterpoint to the position of Carl Schmitt who advocated for the priority of the political concerns of the state. Kelsen was supported in his position by Adolf Merkl and Alfred Verdross, while opposition to his view was voiced by Erich Kaufman, Hermann Heller, and Rudolf Smend. An important part of Kelsen's main practical legacy is as the inventor of the modern European model of constitutional review. This was first introduced in both Austria and Czechoslovakia in 1920, and later in the Federal Republic of Germany, Italy, Spain, Portugal, as well as in many countries of Central and Eastern Europe. As described above, the Kelsenian court model set up a separate constitutional court which was to have sole responsibility over constitutional disputes within the judicial system. Kelsen was the primary author of its statutes in the state constitution of Austria as he documents in his 1923 book cited above.