Guy, Richard K.Unsolved problems in number theory. 3rd edition. - Springer Verlag, 2004. - (Problem books in mathematics).
Capinski, Marek & Zastawniak, T.Probability through problems. - Springer Verlag, 2001. - (Problem books in mathematics).
Souza, Paulo Ney (de) & Silva, Jorge NunoBerkeley problems in mathematics. - Springer Verlag, 1998. - (Problem books in mathematics).
Lam, T.Y.Exercices in classical ring theory. - Springer Verlag, 1995. - (Problem books in mathematics).
Croft, Hallard T. & Falconer, Kenneth J. & Guy, Richard K.Unsolved problems in geometry. Unsolved problems in intuitive mathematics, Volume 2. Second corrected printing. - Springer Verlag, 1994. - (Problem books in mathematics).
Guy, Richard K.Unsolved problems in number theory. 2nd edition. - Springer Verlag, 1994. - (Problem books in mathematics).
Croft, Hallard T. & Falconer, Kenneth J. & Guy, Richard K.Unsolved problems in geometry. (Unsolved problems in intuitive mathematics, Volume 2). - Springer Verlag, 1991. - (Problem books in mathematics).
Croft, Hallard T. & Falconer, Kenneth J. & Guy, Richard K.Unsolved problems in geometry. (Unsolved problems in intuitive mathematics, Volume 2). - Springer Verlag, 1991. - (Problem books in mathematics).
Gelbaum, Bernard R. & Olmsted, John M.H.Theorems and counterexamples in mathematics. - Springer Verlag, 1990. - (Problem books in mathematics).
Berger, M. & Pansu, P. & Berry, J.P. & Saint-Raymond, X.Problems in geometry. - Springer Verlag, 1984. - (Problem books in mathematics).
Guy, Richard K.Unsolved problems in number theory. - Springer Verlag, 1981. - (Problem books in mathematics; 1).