art;
          = 'L':  Lower triangular part.

  LYAPUN  CHARACTER*1
          Specifies whether or not the original Lyapunov equations
          should be solved in the iterative estimation process,
          as follows:
          = 'O':  Solve the original Lyapunov equations, updating
                  the right-hand sides and solutions with the
                  matrix U, e.g., RHS &lt;-- U'*RHS*U;
          = 'R':  Solve reduced Lyapunov equations only, without
                  updating the right-hand 