| Matching Modulo Associativity and Idempotency is NP-Complete Ondrej Klíma 
 June 2000 | 
| Abstract:
We show that AI-matching (AI denotes the theory of an
  associative and idempotent function symbol), which is solving matching word
  equations in free idempotent semigroups, is NP-complete. Available as PostScript, PDF, DVI. |