Which reference/books does AdvApprox package use?

[lavender-lee]

Considering the following two packages,

• AdvApprox
• AdvAppVar2

such as

OCCT/src/AdvApprox/AdvApprox_ApproxAFunction.cxx

Line 484 in 158ed43

Handle(PLib_JacobiPolynomial) JacobiBase = new (PLib_JacobiPolynomial) (WorkDegree, Continuity);

https://github.com/Open-Cascade-SAS/OCCT/blob/158ed439c48389bbba0f4f85f10902d9cba96bca/src/AdvApp2Var/AdvApp2Var_ApproxAFunc2Var.cxx#L345C6-L345C32

I would like to know how to understand this part of the code. Which book should I reference? Thanks very much.