De principis instructione (Instruction for a Ruler) is a Latin work by Gerald of Wales. It is divided into three "Distinctions". The first contains moral precepts and reflections; the second and third deal with the history of the later 12th century, with a focus on the character and acts of king Henry II of England and especially his disputes with the kings of France, Louis VII and Philip II and with his own four sons, Henry the Young King, Geoffrey, Duke of Brittany, Richard, count of Poitou and John Lackland. Gerald was learned in classical, Biblical and medieval Latin literature and in this work cites the Bible, Servius (the commentator on Virgil), Gildas, the Itinerarium Regis Ricardi and many other works. Source: Wikipedia (en)