human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge groups authors who co-authored the same paper.

Details of the hypergraph:
Center hyperedge (induced by source paper "On relating edges in graphs without cycles of length 4"):
  Abstract: Abstract   An edge  xy  is  relating  in the graph  G  if there is an independent set  S , containing neither  x  nor  y , such that    S  ∪  {  x  }    and    S  ∪  {  y  }    are both maximal independent sets in  G . It is an  NP -complete problem to decide whether an edge is relating  [1] . We show that the problem remains  NP -complete even for graphs without cycles of lengths 4 and 5. On the other hand, we show that for graphs without cycles of lengths 4 and 6, the problem can be solved in polynomial time.

Includes members:
  Member "Well-covered graphs without cycles of lengths 4, 5 and 6":
    also connected through other hyperedges:
      (none)

Question: Please tell me which research area the co-authored paper (i.e., the source paper of the center hyperedge) belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Mathematics