theorem
for R being add-associative right_zeroed right_complementable
            Abelian non empty doubleLoopStr,
    a being Element of R,
    i,j being Integer holds i '*' (j '*' a) = j '*' (i '*' a)
proof
let R be add-associative right_zeroed right_complementable
         Abelian non empty doubleLoopStr,
    a be Element of R, i,j be Integer;
thus i '*' (j '*' a) = (i * j) '*' a by Th64 .= j '*' (i '*' a) by Th64;
end;
