This is minor, but the Table of Contents has section numbers that don't always match what's below. For example, the Table of Contents has a link that says:
3.2.3 Subsurface
Although the number in the ToC here says 3.2.3, the section it leads to is numbered 3.7.3.
In fact it appears that there are no sections numbered 3.1 to 3.5. Section 3 Model is followed immediately by section 3.6 Microfacet Model which is labeled as 3.1 in the ToC.