
theorem
  for AG being add-associative right_zeroed right_complementable Abelian
  non empty addLoopStr holds (AG is Uniquely_Two_Divisible_Group iff (for a
  being Element of AG holds (ex b being Element of AG st b + b = a)) & (for a
  being Element of AG st a + a = 0.AG holds a = 0.AG)) by Def1,VECTSP_1:def 18;
