61.   These groups have apparently been isolated from other humans for long periods of time and have no knowledge of the modern world.

62.   They can survive long periods of drought encased in mud, until the next rainy season.

63.   They had to spend long periods apart.

64.   They were convinced there should be no long periods of separation.

65.   They were executed or sentenced to long periods of forced labour.

66.   This probably exacerbated his tendency to long periods of nervous exhaustion, which caused his absence from his parish while he recovered.

67.   This relationship, for very long periods, was in equilibrium.

68.   Thus, the successful model of economic growth has been accompanied by a long period of non-democratic rule.

69.   Viruses tend to mutate and to change their characteristics over long periods of time.