- Ciprian Manolescu (UCLA), the books the problems, http://www.math.ucla.edu/~cm/putnam.html
- Kiran Kedlaya, http://kskedlaya.org/putnam-archive/
- Ciprian Manolescu - A Proof That Some Spaces Can’t Be Cut By: Kevin Hartnett, January 13, 2015, https://www.quantamagazine.org
- Image source (Triangulated): Glen Faught
The books the problems: PUTNAM and BEYOND
Putnam and Beyond, by Titu Andreescu and Razvan Gelca (935-problems), Springer (2007), ISBN 978-0-387-68445-1, 798 p., available online: Sergey V. Lototsky (pdf)
Content: Methods of Proof, Algebra, Real Analysis, Geometry and Trigonometry, Number Theory, Combinatorics and Probability.
"Putnam and Beyond takes the reader on a journey through the world of college mathematics, focusing on some of the most important concepts and results in the theories of polynomials, linear algebra, real analysis in one and several variables, differential equations, coordinate geometry, trigonometry, elementary number theory, combinatorics, and probability. Using the W.L. Putnam Mathematical Competition for undergraduates as an inspiring symbol to build an appropriate math background for graduate studies in pure or applied mathematics, the reader is eased into transitioning from problem-solving at the high school level to the university and beyond, that is, to mathematical research."
From the reviews: "A 935-problem and almost 800-page super-problem book with solutions, whose reading would certainly challenge, attract, and keep really busy any undergraduate student interested in acquiring various problem-solving techniques. ... the array of remarkable problem books has gained a new addition that could be really useful to undergraduate students. ... a book about excellence in mathematics, coming from a long cultural tradition whose history and experience can only help us deepen our understanding of how mathematics could be taught in a more attractive and inquisitive way." (Bogdan D. Suceava and Jack B. Gaumer, The Mathematical Intelligencer, Vol. 33 (2), 2011)
Note: Gazeta Matematica (Mathematics Gazette, Bucharest), proposed by M. Vlada [Real Analysis - solution 549 (p. 589), problem 549 (p. 190)]