How to read what is here

These pages describe how something works. That is not the same as advice fitted to a reader's own position.

Keeping this accurate

The material here is prepared with care, but no promise is made that it is complete, current, or free of error. What is described here can change without this page changing with it.

Linked material

External pages change without notice. A link that was accurate when it was added may point somewhere different now.

Changes

This notice can be updated. The version published here is always the one that applies.

Reporting an error

[email protected] receives correspondence about what is explained on this website.