In the late 11th century, Omar Khayyam wrote Discussions of the Difficulties in Euclid, a book about what he perceived as flaws in Euclid's Elements, especially the parallel postulate.
A finais do século XI, Omar Khayyam escribiu Discusións das Dificultades en Euclides, un libro no que percibiu problemas nos Elementos de Euclides, especialmente no postulado das paralelas.