The morphism axiom for n-angulated categories
  The morphism axiom for n-angulated categories states that a morphism between the bases of two n-angles can be extended to a morphism of n-angles. We show that this axiom is redundant. For triangulated categories, this was proved by J.P. May. 
Emilie Arentz-Hansen, Petter Andreas Bergh, Marius Thaule
math.CT