1. F.N. Abu-Khzam, M.R. Fellows, M.A. Langston, W.H. Suters, Crown structures for vertex cover kernelization. Theory Comput. Syst. 41, 411–430 (2007)
2. B. Aspvall, M.F. Plass, R.E. Tarjan, A linear time algorithm for testing the truth of certain quantified Boolean formulas. Inf. Process. Lett. 8, 121–123 (1979)
3. M.L. Balinski, On maximum matching, minimum covering and their connections, in Proceedings of the Princeton Symposium on Mathematical Programming, ed. by H.W. Kuhn (Princeton University Press, Princeton, 1970), pp. 303–312
4. R. Bar-Yehuda, S. Even, A local-ratio theorem for approximating the weighted vetex cover problem. Ann. Discrete Math. 25, 27–45 (1985)
5. E. Boros, P.L. Hammer, A max-flow approach to improved roof-duality in quadratic 0 − 1 minimization. RUTCOR Research Report RRR 15-1989, RUTCOR (1989)