(en) Richard Drake, Apostles and Agitators : Italy's Marxist Revolutionary Tradition, Harvard University Press, 2009, page 37.
(en) David Goodway, For Anarchism, Routledge, 2013, page 37.
(en) Travis Tomchuk, Transnational Radicals: Italian Anarchists in Canada and the U.S., 1915-1940, University of Manitoba Press, 2015, page 293.
Henri Bartoli, Histoire de la pensée économique en Italie, Publications de la Sorbonne, 2003, page 256.
(en) Gary P. Steenson, After Marx, Before Lenin : Marxism and Socialist Working-Class Parties in Europe, 1884-1914, University of Pittsburgh Pre, page 218.
(en) George Richard Esenwein, Anarchist Ideology and the Working-class Movement in Spain, 1868-1898, University of California Press, 1989, page 107.
Jean Batou, Mauro Cerutti, Charles Heimberg, Pour une histoire des gens sans histoire: ouvriers, exclues et rebelles en Suisse, 19e-20e siècles, Éditions d'en bas, 1995, page 246.
