1. Andreescu, T., Dospinescu, G., Mushkarov, O.: Number theory: concepts and problems, XYZ press (2017). https://bookstore.ams.org/xyz-27
2. Andreescu, T., Saul, M.: Algebraic inequalities: new vistas. MSRI/AMS (2016)
3. Aigner, M., Ziegler, G. M.: Proofs from the BOOK, 6th edn. Springer (2018). https://doi.org/10.1007/978-3-662-57265-8
4. Akopyan, A.V., Zaslavsky, A.A.: Geometry of conics, Mathematical World 26. American Mathematical Society (2007)
5. Beluhov, N.I.: On some pairs of perspective triangles (“O nekotoryh parah perspektivnyh treugoljnikov”), Matematicheskoe Prosveshjenie Ser. 3, 14 (2010), pp. 256–259. https://www.mathnet.ru/rus/mp347