1. A history of pi;Beckmann,1971
2. The arithmetic-geometric mean and fast computation of elementary functions;Borwein;SIAM Review,1984
3. Mathematical manuscripts. Packet 5, Items 6, 8. Parrish Collection;Dodgson,1884
4. Simple facts about circle-squaring;Dodgson,1932
5. Werke;Gauss,1876