human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "On the average Steiner distance of graphs with prescribed properties"
  Abstract: Abstract   The average  n -distance of a connected graph  G ,  μ   n  ( G ), is the average of the Steiner distances of all  n -sets of vertices of  G . In this paper, we give bounds on  μ   n   for two-connected graphs and for  k -chromatic graphs. Moreover, we show that  μ   n  ( G ) does not depend on the  n -diameter of  G .

Connected through hyperedge HE-1 (induced by source paper "Average distance and domination number"):
  with members:
    (none)

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Mathematics