1. The shortest vector problem in L2 is NP-hard for randomized reductions;Ajtai,1998
2. Some APX-completeness results for cubic graphs;Alimonti;Theoret. Comput. Sci.,2000
3. Hardness of set cover with intersection 1;Anil Kumar,2000
4. Complexity and Approximation;Ausiello,1999
5. Approximating low-dimensional coverage problems;Badanidiyuru,2012