1. Gauss, C.F.: Werke, vol. 3, Göttingen, 1866–1933
2. Borwein, J.M., Borwein, P.B.: Pi and the AGM. Wiley, New York (1987)
3. Bracken, P.: An arithmetic-geometric mean inequality. Expo. Math. 19, 273–279 (2001)
4. Batia, R., Li, R.-C.: An Interpolating Family of Means. UT Arlington Preprint Series, 2011-02
5. Carlson, B.C., Vuorinen, M.: Problem 91-17. SIAM Rev. 34, 653 (1992)