Μαρξιστής συγγραφέας (1877-1941). Κυριότερα έργα του είναι: "Bohm-Bawerk's Criticism of Marx", 1904, "Parliamentarianism and the General Strike", 1905, "Finance Capital: A Study of the Latest Phase of Capitalist Development", 1910, "State Capitalism or Totalitarian State Economy", 1940.