I have fixed these pointers (there was previously only the first but with DOI pointing to the second):

Jim Stasheff,

*Homotopy associativity of H-spaces I*, Trans. Amer. Math. Soc.**108**2 (1963) 275-292 [doi:10.2307/1993608]Jim Stasheff,

*Homotopy associativity of H-spaces II***108**2 (1963) 293-312 [doi:10.2307/1993609, doi:10.1090/S0002-9947-1963-0158400-5]