1. Ausiello, C., Crescenzi, P., Gambosi, G., Kann, V., Marchetti-Spaccamela, A., Protasi, M.: Complexity and approximation: Combinatorial optimization problems and their approximability properties. Springer, Heidelberg (2003)
2. Cormode, G.: The hardness of the Lemmings game, or Oh no, more NP-completeness proofs. In: Proceedings of FUN 2004, pp. 65–76 (2004)
3. Demaine, E.D., Hearn, R.A.: Playing games with algorithms: Algorithmic combinatorial game theory. In: Albert, M.H., Nowakowski, R.J. (eds.) Games of No Chance, 3rd edn., vol. 56, pp. 3–56. MSRI Publications (2009)
4. Lecture Notes in Computer Science;M. Forišek,2010
5. Håstad, J.: Some optimal inapproximability results. In: Proceedings of STOC 1997, pp. 1–10 (1997)