Although the IEEE documentation can be purchased, many (in particular government) resources reference the IEEE as being a format used. This best practices gov document makes reference to the IEEE standards for requirements management and presents a clears and well laid out requirements traceability matrix outline.

The Wikipedia entry for Requirements Traceability is concise and precise. The idea of structural evolution rather than chronological is especially interesting. The main points of tracing requirements to design and testing is also well described.

We really like finding and referencing government testing (and software quality) resources and this one really spells out the definition of requirements traceability with reference to the typical water fall model. Although only 3 pages in length this guide really packs some useful practical advice on defining a requirements traceability document.