Figure 7.

Two sets of possible configurations of an undecided variable gadget and the corresponding transformation of the covering. (Note that if edge {c, c'} is also missing in either initial configuration on the left, that the corresponding configuration on the right still applies, since c and c' do not intersect any vertex outside this variable gadget, and the number of hyperedges removed has not increased.)

Ma┼łuch et al. BMC Bioinformatics 2012 13(Suppl 19):S11   doi:10.1186/1471-2105-13-S19-S11