handbook/*

• Use trademark entities.
• Add trademark attributions.
• Always use correct case for trademarks.
• Don't join trademarks with other words, e.g. using hyphens.
• Don't use trademarks as nouns (e.g. don't use "Windows NT's").

diskless-x/article.sgml:

• While I'm here anyway add trademark tags for all trademarks, now that the stylesheet handles it right.

trademark.ent:

• Add entities for more trademarks / companies.

Also rename the 3Com trademark entity from t3com to tm.3com. This
should make the entity naming convention a bit more consitent. This is
done now since the entity is not used too many places yet.