41.   The difficulty with habits is that they are difficult to change.

42.   The economic results of the reforms are difficult to judge.

43.   The economic results of the reforms are very difficult to judge.

44.   The number of trips that can be expected for a spacecraft that transports water back from an asteroid is difficult to estimate.

45.   The sculpture is heavy and very difficult to move.

46.   The sensitive souls found her more difficult to stomach.

47.   The third factor, hygiene, is perhaps the most insidious and difficult to control.

48.   The value of the work undertaken by informal carers is difficult to estimate with precision.

49.   There was, however, a widespread feeling that very large armies were undesirable because they were difficult to supply and manoeuvre.