Spectral Theory of Graphs in Chemistry. 1. Projection Operators and Canonical Numeration of Graph Vertices. - Ivan V. Stankevich; Elena G. Gal'pern; Anatolii L. Chistyakov; Igor I. Baskin; Mariya I. Skvortsova; Nikolai S. Zefirov; Oleg B. Tomilin (J. Chem. Inf. Comput. Sci., 1994)