11. Extremal combinatorics studies extremal questions on set systems.12. Extremal combinatorics studies extremal questions on set systems. 13. Ramsey theory is another part of extremal combinatorics. 14. Until recently, prospects for useful extremal principles in this area have seemed clouded. 15. Other writers have also felt that prospects for general global extremal principles are clouded. 16. The condition allows one to prove that a corner exists along a given extremal . 17. Extremal states are usually called pure states.18. Extremal black holes have vanishing surface gravity.19. Several foundational results in extremal graph theory are questions of the above-mentioned form. 20. The two areas that interest him most are extremal graph theory and random graph theory.
