“…The analytical theory for differential-algebraic equations has been developed quite far in the last two decades, and also a wide variety of numerical methods are available, see [8, 12, 13, 21, 29-31, 33, 36, 38, 45, 49, 50]. Furthermore, the theory and also numerical techniques have been extended to control problems [10,15,16,26,27,34,36,37,51].…”