Marx Brothers stage during the middle of a Groucho monologue to see if Groucho would be thrown off. However, to the audience's delight, Groucho merely reacted by commenting, "First time I ever saw a taxi hail a passenger". When Harpo chased the girl back in the other direction, Groucho calmly checked his watch and ad-libbed, "The 9:20's right on time. You can set your watch by the Lehigh Valley." The brothers' vaudeville act had made them stars on Broadway under Chico's management and with Groucho's creative direction—first with the musical revue "I'll Say She Is" (1924–1925) and then with two musical comedies:
Karl Marx and the Close of His System has been seen as one of the most important discussions of Marx's economic theories, along with Rudolf Hilferding's "Böhm-Bawerk's Criticism of Marx", a defense of Marx against Bawerk. Bawerk's work is the "classical" critique of "Capital". Most subsequent critiques of Marxist economics have repeated Bawerk's arguments. Marxist economist Ernest Mandel identifies "Karl Marx and the Close of His System" as part of a literature, beginning with German social democrat Eduard Bernstein, that criticizes the dialectical method Marx borrowed from Georg Wilhelm Friedrich Hegel as "useless", "metaphysical", or "mystifying." He faults Böhm-Bawerk and the other critics for what he regards as