Perhaps you should try some spelling variations:
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"
"towler graining methods algorithm" » "towler learning methods algorithm", "towler learning method algorithm", "towler making methods algorithm", "tower graining methods algorithm", "bowler graining methods algorithm"

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• If you are trying to use Boolean operators, they must be ALL CAPS: (("towler graining methods algorithm") OR ("modified notion approximation algorithms"))~.
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