Adding the subscript yz|w|x to an internal node claiming the butterfly quartet wx|yz, indicates that the leaves y and z are found in a single subtree of the internal node, while the leaves w and x are found in different subtrees. For example, considering the quartet ab|cd, v and v' in Fig. 7 are written as vab|c|d and v′ab|c|d MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacuWG2bGDgaqbamaaBaaaleaacqWGHbqycqWGIbGycqGG8baFcqWGJbWycqGG8baFcqWGKbazaeqaaaaa@3691@.