Perhaps you should try some spelling variations:
"modified objective approximation algorithm" » "modified objective approximation algorithms"
"modified static estimation algorithmss" » "modified static estimation algorithms", "modified static estimation algorithm", "modified static optimization algorithms", "modified static optimization algorithmss"

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