1. G. M. Kelly, "On Mac Lane's conditions for coherence of natural associativities, commutativities, etc.", J. Algebra, 4(1964), 397–402.
2. G. M. Kelly and S. Mac Lane, "Coherence in closed categories", J. Pure Appl. Algebra, 1(1971), 97–140.
3. M. Laplaza, "Coherence for categories with associativity, commutativity and distributivity", Bull. Amer. Math. Soc. (to appear).
4. S. Mac Lane, "Natural associativity and commutativity", Rice Univ. Studies, 49(1963), 28–46.
5. S. Mac Lane, "Coherence and canonical maps', Symposia Mathematica, IV(1970), 21–241.