We just note where the information from each entry came from, or each part of the entry. Now I didn't write the LV-426 entry (in fact, now that you've brought it to my attention, I'll edit it to include the stuff from the Res novel), but if you'll notice underneath the AVP info, it does say that the info should not be considered canon.
Now this isn't the way I plan on doing it, I plan on just notating where each section of an entry comes from, and noting where they contradict, so that readers can make their own judgments on 'canon'.