"The Zoological Record Thesaurus contains controlled terms used to index records. It also contains uncontrolled terms as entry points to controlled (preferred) terms. The five major hierarchies in the thesaurus are: Subject; Geographical; Palaeontological; Systematic; Taxa Notes. You can expand each hierarchy to browse for controlled terms and to see their positions in the hierarchy. You can also search the entire combined thesaurus to find the appropriate controlled term(s) for your search."