added pointer to:

- R. F. C. Walters,
*A categorical approach to universal algebra*, Ph.D. Thesis (1970) [anu:1885/133321]

Fixed a small spacing issue that made what should be “algebras over algebraic theories” look like “algebras overalgebraic theories”.

Joe Driscoll

]]>Edited the text in the Idea-section, such as to make the terms *monoidal category*, *monoid objects*, *module objects* appear.