Level 1	-	Confirmed by Chemical Abstracts Service or the developing company as the correct structure.
Level 2	-	Structure identified in Merck index or published by WHO or USAN council.
Level 3	-	Structure identified in a peer-reviewed journal.
Level 4	-	Structure identified in a non-peer reviewed printed source, such a meeting handout, press release, or non-company website.
Level 5	-	Hand-drawn structure from a conference, or structure based on an informed decision by a Thomson Scientific patent analyst made by correlating unambiguous chemical information from the company's patent filings with information from other sources such company publications and communications.