41.   When a complementary wavelength is used the response to the small spot only occurs at the offset of the stimulus.

42.   If headaches only occur at night, lack of fresh air and oxygen is often the cause.

43.   Combustion may occur at high temperatures.

44.   The event is scheduled to occur at noon tomorrow.

45.   The accident occurred at a busy intersection.

46.   The best milk production occurs at the same time that new plant growth is available.

47.   The real dividing line between continents and oceans occurs at the foot a steeper slope.

48.   Mikhail Gorbachev, the Soviet President, said that unification occurs at the watershed of two epochs.

49.   The incident occurred at the end of a week of unusually heavy artillery and small-arms skirmishing between Indian and Pakistani troops across the Kashmir border.

50.   I explained in my statement in the annual report about the management reorganisation which occurred at the end of nineteen eighty nine.