Perhaps you should try some spelling variations:
"modified positive solution algorithm" » "modified positive evolution algorithm", "modified positive convolution algorithms", "modified positive evolutionary algorithm", "modified passive solution algorithm", "modified adaptive solution algorithm", "modified positive solutions algorithm"
"modified average approximation algorithms" » "modified coverage approximation algorithms"

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• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified average approximation algorithms") OR ("modified positive solution algorithm"))~.
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