Fixes to compile back matter

Commented out indexing of division symbol (p. 36).
Removed \\ in bibliography in failed attempt to fix natbib error.
Revert "Fixes to compile back matter"

This reverts commit 59e5a53bd0bc5cd30596852bcbc525d85653d70e.
Merge branch 'master' of https://github.com/bartsnapp/NumbersAndAlgebra