Giovanni d'Andrea or Johannes Andreæ (1270 × 1275 – 1348) was an Italian expert in canon law, the most renowned and successful canonist of the later Middle Ages. His contemporaries referred to him as iuris canonici fons et tuba ("the fount and trumpet of canon law"). Most important among his works were extensive commentaries on all of the official collections of papal decretals, papal judgments in the form of letters to delegated judges that were at the core of canon law. Source: Wikipedia (en)