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: "Higher-order orderings for normal rewriting"
  Abstract: We extend the termination proof methods based on reduction orderings to higher-order rewriting systems a la Nipkow using higher-order pattern matching for firing rules, and accommodate for any use of eta, as a reduction, as an expansion or as an equation. As a main novelty, we provide with a mechanism for transforming any reduction ordering including beta-reduction, such as the higher-order recursive path ordering, into a reduction ordering for proving termination of rewriting a la Nipkow. Non-trivial examples are carried out.

Connected through hyperedge HE-1 (induced by source paper "Polymorphic higher-order recursive path orderings"):
  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