However, Gui's best-known works are those related to his inquisitorial career: "Liber sententiarum," a comprehensive register of the sentences he delivered, and "Practica inquisitionis heretice pravitatis", a comprehensive inquisitor's manual. Inquisitors had no standardised or formal training, although they were often educated in theology or law, and practical guides to inquisitorial activities emerged as a distinct literary genre in the late twelfth century. Gui's manual consisted of five books: the first three were formularies, providing templates to be used to deliver sentences during 'general sermons', and the fourth reproduced documents outlining and confirming the powers of the inquisitor (such as papal and conciliar legislation, and royal decrees). The fifth and most famous book provided descriptions of the beliefs and practices of heretics such as Cathars (referred to as 'modern Manicheans'), Waldensians, Pseudo-Apostles, Beguines, and relapsed Jews, in addition to guidance for inquisitors on the best methods of interrogation for each group (including advocating torture if necessary). This was the first inquisitor's manual to refer specifically to penalties for relapsed Jews.