20. Modesto, Alcides and Ribeiro, Zezéu. "Nada deve parecer impossível" [Carta à Juventude]. N.p.:, 1990 August.

20. Modesto, Alcides and Ribeiro, Zezéu. "Nada deve parecer impossível" [Carta à Juventude]. N.p.:, 1990 August., Box: 17. Eduardo Sarno Collection of Leftist Movements in Brazil, 2002-03. Benson Latin American Collection, The University of Texas at Austin. https://archives.lib.utexas.edu/repositories/4/archival_objects/374103 Accessed September 27, 2026.