On the Numbers of Representations of a Number as a Sum of $2r$ Squares, Where $2r$ Does not Exceed Eighteen

Question

I am reading the article "Mathematicians Chase Moonshine’s Shadow" [1], and want to follow up on one of its sources "On the Numbers of Representations of a Number as a Sum of $2r$ Squares, Where $2r$ Does not Exceed Eighteen" by J. W. L. Glaisher [2]. Since I can't get my hand on the original, what would be the best book that summarizes the results of [2]?

[1] https://www.quantamagazine.org/mathematicians-chase-moonshine-string-theory-connections-20150312/

[2] https://londmathsoc.onlinelibrary.wiley.com/doi/pdf/10.1112/plms/s2-5.1.479

Answer 1

After digging through many books, the best I found on the subject are:

1. Grosswald, E. (1985). Representations of integers as sums of squares. New York: Springer.
2. Moreno, C. J., & Wagstaff, S. S. (2006). Sums of squares of integers. Boca Raton: Chapman & Hall/CRC.

Both books have references to Glaisher and his work. Both books expand on the subject in detail, using results in the field by other mathematicians (besides Glaisher).