Improved worst-case complexity for the MIN 3-SET COVERING problem

We consider MIN SET COVERING when the subsets are constrained to have maximum cardinality tree. We propose an exact algorithm whose worst case complexity is bounded above by O (1.3957n) This is an improvement, based on a refined analysis, of a former result (O(1.4492n)) by F. Della Croce and V. TH. Paschos, Computing optimal solutions for the MIN 3-SET COVERING problem, Proc. ISSAC'05, LNCS 3827, pp. 685-692.