Angelo was a humanist and Milanese scholar who moved to Ferrara in 1438. Decembrio's connection to Leonello comes from his work he wrote before 1447, the "De Politia Litteraria Variisque Poetae Virgilli Laudbibus", which was a dialogue divided into three volumes; four more books were added around 1462. The treatise was about how to successfully sustain the refinement of literature/politia litteraria in a courtly environment. The work also focused on the description of Ferrara; Angelo also included his thoughts about Leonello within the overall depiction. The text description reads (in translation) that: "the city of Ferrara, with its streets, gardens and villas and, in the heart of the city, the d’Este court, whose greatest attribute is the enormous library. The library, with its sumptuous furnishings and judicious choice of volumes (with a distinct preference for classical literature) is the perfect image of what constitutes a vital sector of the prince’s investment in culture in the second half of the fifteenth century. The d’Este library, passionately and painstakingly supplemented by Leonello…it is a place of authentic cultural reference, but above all… the prestige of the prince as patron of the arts".