70. This problem in essence involves using x to obtain a solution.

71. An additional research issue to be tackled is ....

72. Some important issues in developing a ... system are discussed

73. The three prime issues can be summarized:

74. The situation leads to the problem of how to determine the ...

75. There have been many attempts to

76. It is expected to be serious barrier to

77. It offers a simple solution in a limited domain for a complex