The purpose of this website

The writing here describes how a subject works. That is not the same as advice fitted to a reader's own position.

Mistakes and changes

Where a figure, rule, or mechanism matters to a decision, check it against the primary source before relying on it. Nothing here is warranted as fit for that purpose.

Where links lead

A link may lead to a website someone else runs. What those websites publish, and how they treat visitors, is their responsibility and not this one's.

Reporting an error

If you need to raise something about the material published here, use [email protected].