41.   The lack of economic statistics has made life difficult for economists and money managers for the past few weeks.

42.   The light comes right through our curtains and makes sleeping difficult.

43.   The limited body of mathematical results describing chaotic control networks makes generalization difficult.

44.   The medicine can make it difficult to remain alert.

45.   The need to understand the meaning of behaviour also makes it difficult to predict how individuals will behave.

46.   The penal laws in force at the time, however, made mixed Marriages difficult, if not impossible.

47.   The problem of tracing the invention of enamel is made more difficult by failing to distinguish it more certainly from glass.

48.   The rise of credit derivatives makes it difficult to determine which banks are exposed to a particular risk.