This section covers Kelsen's years in Austria, Germany, Czechoslovakia and Switzerland. While still in Austria, Kelsen entered the debate on the versions of Public Law prevailing in his time by engaging the predominating opinions of Jellinek and Gerber in his 1911 Habilitation dissertation (see description above). Kelsen, after attending Jellinek's lectures in Heidelberg oriented his interpretation according to the need to extend Jellinek's research past the points which Jellinek had set as its limits. For Kelsen, the effective operation of a legal order required that it be separated from political influences in terms which exceeded substantially the terms which Jellinek had adopted as its preferred form. In response to his 1911 dissertation, Kelsen was challenged by the neo-Kantians, originally led by Hermann Cohen, who maintained that there were substantial neo-Kantian insights which were open to Kelsen, which Kelsen himself did not appear to develop to the full extent of their potential interpretation as summarized in the section above. Sara Lagi in her recent book on Kelsen and his 1920s writings on democracy has articulated the revised and guarded reception of Jellinek by Kelsen. Kelsen was the principal author of the passages for the incorporation of judicial review in the Constitutions of Austria and Czechoslovakia during the 1910s largely on the model of John Marshall and the American Constitutional experience.