Enee Silvii Piccolominei epistolarium seculare : complectens De duobus amantibus, De naturis equorum, De curialibus miseriis / post Rudolf Wolkan iterum recognovit edidit Adrianus van Heck. - Pius PP. II, 1405-1464. (OLS)http://pul/name/6154; Heck, Adrianus van, 1923- (OLS)http://pul/name/5101; Wolkan, Rudolf. (OLS)http://pul/name/90045 (Biblioteca Apostolica Vaticana, 2007)