# PERCEPTUAL RULES

_Perceptual rules_ help to clearly relay content by using an appropriate visual
design. They comprise the second part of this guide with the rule sets
[EXPRESS](04-express.md), [SIMPLIFY](05-simplify.md),
[CONDENSE](06-condense.md), and [CHECK](07-check.md).

The perceptual rules are based on the work of authors such as William
[Playfair](https://www.amazon.com/dp/0521855543), Willard Cope
[Brinton](https://www.amazon.com/dp/1290860955), Gene
[Zelazny](https://www.amazon.com/dp/007136997X), Edward
[Tufte](https://www.amazon.com/dp/1930824130), and Stephen
[Few](https://www.amazon.com/dp/0970601972). All of these rules owe wide
acceptance to their scientific, experimental, and/or practical experience basis.