Sukumar Mondal Madhumangal Pal Tapan Kumar Pal An Optimal Algorithm to Solve 2-Neighbourhood Covering Problem on Interval Graphs. 189-204 2002 79 Int. J. Comput. Math. 2 http://taylorandfrancis.metapress.com/openurl.asp?genre=article&issn=0020-7160&volume=79&issue=2&spage=189 db/journals/ijcm/ijcm79.html#MondalPP02