In Brewer et al. we find mentioned an overtone. To understand the nature of this overtone, let us consider the article by "Since the 1930s many kinds of models of the structure of liquid water have been proposed to account for its properties". As previously told, two main models exist and are usually designated as continuum model and mixture model. "Models belonging to the former group assume that all water molecules in the liquid continue to be hydrogen bonded to neighboring water molecules, but that the intermolecular links can be bent and stretched to produce irregular and varied networks [See the in . The latter models share the premise that liquid water is a mixture of several distinct molecular species called water clusters ((H2O)n). All mixture models require the existence of broken hydrogen bonds: in some models they occur at the boundaries of postulated molecular clusters of different kinds. One of the simplest models included in the mixture models is the two-structure model. Such a model has recently been proposed by Benson and Siebert …" .