Besides Section 8 (Tank Vehicles), which other sections of the CDL manual does the manual say a tanker endorsement candidate should also study?

AAMVA CDL Manual, Section 8 introduction (p. 8-8-1)

The tanker knowledge test doesn't exist in isolation. Because it draws on driving-safety, air-brake, combination-vehicle, and hazmat material too, a candidate who studies only the tank-specific chapter can still be caught off guard by cross-topic questions on the real exam.