Gaya APA

II, J, P. (1987). Encyclical letter 'Sollicitudo Rei Socialis' to the bishops, priests, religious families, sons and daughters of the Church and all people of good will for the twentieth anniversary of 'Populorum Progressio'. . Vatican City: Vatican City Libreria Editrice Vaticana.

Gaya MLA

II, Joannes, Paulus. "Encyclical letter 'Sollicitudo Rei Socialis' to the bishops, priests, religious families, sons and daughters of the Church and all people of good will for the twentieth anniversary of 'Populorum Progressio'. ". Vatican City: Vatican City Libreria Editrice Vaticana, 1987. Buku.