Fan R. K. Chung Zoltán Füredi M. R. Garey Ronald L. Graham On the Fractional Covering Number of Hypergraphs. 45-49 1988 1 SIAM J. Discret. Math. 1 db/journals/siamdm/siamdm1.html#ChungFGG88 https://doi.org/10.1137/0401005