In the following we refer to standard complexity classes
(see [277]). We recall that a function *t(n)* is
`quasi-polynomial' if a constant *c* exists such that
and we denote by QP, QNP, and QR the analogues of the usual complexity
classes in the quasi-polynomial time domain.

- NPO problems: definitions and preliminaries
- Terminology for graph problems
- Approximate algorithms and approximation classes
- Completeness in approximation classes
- A list of NPO problems
- Improving the compendium