Below are some useful links related to mathematical problem solving, including a link to the William Lowell Putnam Mathematical Competition, a nationwide mathematics contest for undergraduates. All students officially registered in the class are required to participate in this competition.
William Lowell Putnam Mathematical Competition
Previous Putnam Problems and Solutions
Kedlaya, Kiran Sridhara, Bjorn Poonen, and Ravi Vakil. The William Lowell Putnam Mathematical Competition 1985–2000 Problems, Solutions, and Commentary. MAA problem books series. American Mathematical Society; UK ed. edition, 2002. ISBN: 9780883858271.
Additional Books Helpful for Preparation
Larson, Loren C. Problem-Solving Through Problems (Problem Books in Mathematics). New York, NY: Springer-Verlag, 1983. ISBN: 9780387908038.
Gelca, Razvan, and Titu Andreescu. Putnam and Beyond. New York, NY: Springer-Verlag, 2007. ISBN: 9780387257655.