Perhaps you should try some spelling variations:
"modified multiobjective estimation algorithm" » "modified multiobjective optimization algorithm"
"modified policy approximation algorithms" » "modified complexity approximation algorithms", "modified one approximation algorithms", "modified time approximation algorithms"

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