Originally published as:
 
Ph.D. thesis, Columbia University, 1963
and
in Reports of the Midwest Category Seminar II, 1968, 41-61, 
© Springer-Verlag, and used by
permission.  
The authors comments are ©
F. William Lawvere, 2004.
Keywords: Algebraic theories, functorial semantics
2000 MSC: 18.10
 
Republished in:
Reprints in Theory and Applications of Categories, 
No. 5 (2004) pp  1-121
 
http://www.tac.mta.ca/tac/reprints/articles/5/tr5.dvi
http://www.tac.mta.ca/tac/reprints/articles/5/tr5.ps
http://www.tac.mta.ca/tac/reprints/articles/5/tr5.pdf