In 1546, three years after the Fabrica, he wrote his Epistola rationem modumque propinandi radicis Chynae decocti, commonly known as the Epistle on the China Root. Source: Internet
Further reading * Friar Elias, Epistola Encyclica de Transitu Sancti Francisci, 1226. Source: Internet
In his anger he appealed to force, and his Epistola ad Carolum V (18 February 1521) called on the emperor to take measures against Luther, an appeal soon answered by the Edict of Worms (May 1521). Source: Internet