 subset ![ $$U' \\subseteq \\mathcal{S}$$ ](A000000_0_En_0_Chapter_IEq00.gif).  Property 0.0.  Let ![ $$i^{{\\ast}}\\in \\mathcal{S}$$ ](A000000_0_En_0_Chapter_IEq00.gif) be the first element selected in line 0 of the greedy algorithm in Figure 0.0. The