Acz\'elian n-ary semigroups
  We show that the real continuous, symmetric, and cancellative n-ary semigroups are topologically order-isomorphic to additive real n-ary semigroups. The binary case (n=2) was originally proved by Acz\'el (1949); there symmetry was redundant. 
Miguel Couceiro, Jean-Luc Marichal
math.RA math.FA