-@BOOK{AMPL,
- AUTHOR = "Robert Fourer and David M. Gay and Brian W. Kernighan",
- TITLE = "AMPL: A Modeling Language for Mathematical Programming",
- PUBLISHER = "Cengage Learning",
- YEAR = "November 12, 2002",
- edition = "2nd",
-
-}
-
-@ARTICLE{glpk,
-author = {Andrew Makhorin},
-title = {The GLPK (GNU Linear Programming Kit)},
-journal = {Available: https://www.gnu.org/software/glpk/},
-year = {2012}
+@article{gentili2013,
+year={2013},
+journal={Optimization Letters},
+volume={7},
+number={1},
+title={α-Coverage to extend network lifetime on wireless sensor networks},
+publisher={Springer-Verlag},
+author={Gentili, Monica and Raiconi, Andrea},
+pages={157-172},