**Comments:**

The only formal prerequisite for the first article is familiarity with angular momentum in quantum mechanics as explained in the section “Angular momentum in quantum mechanics." However, most of the content can be understood without this prerequisite as long as one is familiar with the concept of a matrix. The other articles should be read in the listed order. The second half of “Non-Abelian gauge theory” assumes familiarity with tensors as presented in the first six sections of “A relatively short introduction to general relativity.” The article “Wilson line and Wilson loop” is important since the “loop” in loop quantum gravity is the Wilson loop.