1. Akopyan, A.: Geometry in Figures. A. Akopyan, Moscow (2011)
2. Aleksandrov, P.S., Markushevich, A.I., Chintshin, A.J. (Eds.): Enzyklopädie der Elementarmathematik, Band IV, Geometrie. Deutscher Verlag der Wissenschaften, Berlin (1969). Russian original: Moscow, 1963
3. Alonso, J., Martini, H., Spirova, M.: Minimal enclosing discs, circumcircles, and circumcenters in normed planes (Part I). Comput. Geom. 45(5–6), 258–274 (2012)
4. Alsina, C., Nelsen, R.: When Less is More: Visualizing Basic Inequalities. Dolciani Mathematical Expositions, vol. 36. Mathematical Association of America, Washington, DC (2009)
5. Altshiller-Court, N.: Modern Pure Solid Geometry, 2nd edn. Chelsea Publishing Co., New York (1964). First edition: Macmillan Company, 1935