Directories organize information resources alphabetically or by subject .
Subject directories often present their resources in a hierarchical arrangement, moving from the general to the more specific. Here is one example of a topical index that is hierarchically arranged. Return to first slide 15 Minute Series Home 15 Minute Series Search Click the icon at the top of the page to go to the next slide. This material may be quoted or reproduced provided appropriate credit is given and copyright notice is retained.