Some Notes on Closure Concepts for Claw-Free Graphs

摘要

We discuss the relationship between Ryjacek's closure and the K4-closureintroduced duced by the first author. Our main result deals with a variation on the K-4-closure. It implies a simpler proof of Ryjacek's closure theorem, and yields a more general closure concept which is not restricted to claw-free graphs only.