Indices of reciprocal properties or Harary indices

Reciprocal topological properties are used for building up novel indices referred to as Harary indices. They are defined by the aid of matrix algebra and examplified on appropriate sets of graphs. Analytical relations for calculating the indices, defined both on the basic and the reciprocal property, in particular classes of graphs are derived. The correlating and discriminating ability as well as the limitations of these indices are discussed.