“…Being the molecular DF positive definite, the nature of the similarity integrals (Bultinck, Gironés, & Carbó-Dorca, 2005;Bultinck, Van Damme, & Carbó-Dorca, 2009;Carbó, Besalú, Amat, & Fradera, 1996;Carbó, Calabuig, Vera, & Besalú, 1994;Carbó & Besalú, 1995;Carbó & Calabuig, 1990;Carbó-Dorca & Besalú, 1998;Carbó-Dorca, 2013d), a basic notion in QS, is attached in any circumstance to a measure. This fact, resulting into the similarity measures definite positiveness, encompassed the discussions about the use of similarity matrices in QQSPR applications (Carbó-Dorca & Besalú, 1998;Carbó-Dorca, 2013d, 2014a, 2014b, and has to be considered the source of a large variety of mathematical definitions and algorithms (Carbó-Dorca & Barragán, n. d.;Carbó-Dorca & Besalú, 2012a;Carbó-Dorca & González, 2016;Carbó-Dorca, 2013b, 2015a) related to the QS problems.…”