“…Recently, in addition to the use of variable connectivity indices [35][36][37][38][39][40][41][42][43], several different flexible molecular descriptors have been considered in the literature, including the use of variable paths weights [44,45], variable distance related indices [46,47], and other variable descriptors [48]. Thus, we may well be at the beginning of a novel direction in structure-property-activity studies that will be dominated by the use of variable molecular descriptors that not only lead to better regressions with fewer molecular descriptors in comparison with regressions using "fixed" descriptors, but, because variable descriptors offer novel interpretation to the descriptors [49], may also offer guidance in the refinement of molecular models, as will be explained later in this article.…”