His Problemas económicos de la revolución social española ... 1934.
His Colectividades libertarias en España, 1972-1974 t.p. (Gastón Leval)
Souchy, A. Kollektivierungen in Spanien, 1936-1939, 1981 t.p. (G. Leval)
Nat. Lib. of France auth. file, 18 Jan. 2010 (hdg.: Leval, Gastón, 1895-1978; pseud of Pierre Piller; born 20 Oct. 1895; died 8 Apr. 1978; French author; wrote in French and Spanish)
Anarchy Archives website, 18 Jan. 2010 (Pedro R. Piller, born 1895 in France, went under the pseudonym of Gaston Leval; he was a French anarchist during the Spanish Civil War and was the son of a French Communard; died 8 Apr. 1978)
Wikipedia (French), 18 Jan. 2010 (Gaston Leval, pseudonym of Pierre Robert Piller; born 20 Oct. 1878, died 8 Apr. 1978; anarcho-syndicalist and historian of the Spanish revolution)
Wikipedia (English) and Wikipedia (Spanish), 18 Jan. 2010 (Gaston Leval; anarcho-syndicalist, combatant and historian of the Spanish Revolution; born Robert Pillar, 20 Oct. 1895; the son of a French Communard, he escaped to Spain in 1915 to avoid conscription)