Euclid (300 BC) was a Greek mathematician who brought together previous mathematical work and extended it. He recorded this in a systematic way in thirteen books called the Elements of Geometry. Six books deal with the geometry of planes, four with the theory of numbers and three with the geometry of solid objects. Euclid's work was translated into many different languages and it dominated mathematics for over 2000 years. The Elements of Geometry were the first mathematics books to be printed. Some errors were found in Euclid's work by the 19th century. However, most of his findings remain valid.