1. On the chain algebra of a loop space;Adams, J. F.;Comment. Math. Helv.,1956
2. H. Cartan, Séminaire, Ecole Normale Supérieure, 1954-55.
3. On 𝐻-spaces with two non-trivial homotopy groups;Copeland, Arthur H., Jr.;Proc. Amer. Math. Soc.,1957
4. P. J. Hilton, Homotopy theory and duality (mimeographed), Cornell University, 1959.