 reserve x,y,X,Y for set;
reserve G for non empty multMagma,
  D for set,
  a,b,c,r,l for Element of G;
reserve M for non empty multLoopStr;
reserve H for non empty SubStr of G,
  N for non empty MonoidalSubStr of G;

theorem
  D-concatenation is having_a_unity &
  the_unity_wrt (D-concatenation) = {} &
  D-concatenation is associative
proof
  multMagma(#D*,D-concatenation#) = D*+^ by Def34;
  hence thesis by Th60;
end;
