Table of Contents

Definitions and basic results.- Some recently solved problems.- Some (catenary) chain conjectures.- The chain conjecture.- The Depth Conjecture and the weak Depth Conjecture.- The H-conjecture.- The descended GB-conjecture and the GB-conjecture.- The strong avoidance conjecture and the avoidance conjecture.- The upper conjecture.- The taut-level conjecture.- The catenary chain conjecture.- The normal chain conjecture.- Comments on (3.3.1) and conjecture (K).- Some examples.- Some related questions.