1. S. Alagić, Natural state transformations, Department of Computer and Information Science Technical Report 73B-2, Univ. of Mass., 1973.
2. — Algebraic aspects of ALGOL 68, Computer and Information Science Technical Report 73B-5, Univ. of Mass., 1973.
3. — Categorical theory of tree transformations, this volume.
4. H. Appelgate, Acyclic models and resolvent functors, dissertation, Columbia University, 1965.
5. B. D. O. Anderson, M. A. Arbib and E. G. Manes, Finitary and infinitary conditions in categorical realization theory, to appear.