Minor formatting
Removed "fields" from example because fields are not algebraic.

The structure of a field is not an algebraic structure because it
involves an apartness relation. While we could still make everything
work for fields, we probably don't want to drag apartnes in at this
point. So it seems easier to just delete fields from the list.
Conforming 2.14 to book standards, minor changes to content
Making sure all equations are referred to the same way with `\eqref`.