How to Write a Good Requirement

> Is the requirement free of implementation? (Requirements should state WHAT is needed, NOT HOW to provide it; i.e., state the problem not the solution. Ask, “Why do you need the requirement?” The answer may point to the real requirement.)

Sounds obvious but always worth repeating.

I've seen system requirements specs that were detailed implementation design documents and, worse I have seen system engineers ask software engineers how they had implemented something so that they could write a matching system requirements (too detailed, of course) after the fact!

What document is this a part of? I see only appendices and no way to navigate to the top level of the document.