“…ξ c was introduced by Sharma, Goswami, and Madan [17], ξ d by Gupta, Singh, and Madan [7], and DD by Dobrynin and Kochetova [6] and by Gutman [8]. These three topological indices are well investigated, selected contrubutions to the eccentric connectivity index are [10,13,22], to the eccentric distance sum [1,14,21], and to the degree distance [15,18,19]. The three invariants were also compared to other invariants, cf.…”