What is the source or reference of the Affygility Solutions' control banding system?

The original source of the Affygility Solutions' control banding system was adapted from the following reference:

Heidel, D.S. (2000). Industrial Hygiene Aspects of Pharmaceutical Manufacturing. In J.P. Wood (Ed.) Containment in the Pharmaceutical Industry (pp.. 26-27). New York, NY,  Marcel Dekker, Inc.

where on page 27, the following table was presented:

No matter what containment options are considered, it is critical to understand the following points.

• Since the year 2000 there have been numerous improvements in containment technologies. Today, there are many more containment options for handling Category 3 or higher compounds. Pharmaceutical manufacturers should check with their local equipment vendors to determine what containment options are available.
• The selection of the primary engineering controls, administrative controls, and personal protective equipment needs to be based on a site-specific risk assessment.
• Once you have the numerical OEL, the control band or occupational health category is no longer important. What is important is knowing that your equipment controls exposures to below the occupational exposure limit. This must be done by performing site-specific industrial hygiene or surrogate monitoring.
• There are many different control banding systems, including the Affygility Solutions, Pfizer, Merck, Roche, SafeBridge, and many others. There is no global alignment in the systems because of the variety of compounds and equipment in use.