Camara, Helder (2015) [2009], "15a Circular (Reservada) - Roma 24/25.9.1965", in Luiz Carlos Luz Marques; Roberto de Araújo Faria (eds.), Dom Helder Camara Circulares Conciliares (in Portuguese), vol. I, Recifé (PE), Brazil: Companhia Editora de Pernambuco, ISBN9788578581558, retrieved 9 April 2016