(a) The variable gadget for variable x with literal vertices x1, x2 and ¬x, as well as the four auxiliary vertices x', x'', x''', x'''' that do not appear in any other hyperedge of . (b) 2-clause gadget with literal vertices p and q, as well as the two auxiliary vertices c and c' that do not appear in any other hyperedge of Hϕ. (c) 3-clause gadget with literal vertices p, q and r.
Maňuch et al. BMC Bioinformatics 2012 13(Suppl 19):S11 doi:10.1186/1471-2105-13-S19-S11