Fig. 13
From: Investigating the complexity of the double distance problems
Types of double-line: terminal, balanced and unbalanced links. The yellow solution that in cases (i–ii) leaves v unselected and in cases (iii–iv) leaves u and v unselected can be fixed so that an independent set of the adjacent unsaturated path-line(s) can start at \(v'\) (and \(u'\)). In cases (v–vi) either the yellow or the green solution will be fixed later; it will be the one compatible with the selected independent set of the unsaturated path-line ending in \(u'\) concatenated to the one starting in \(v'\)