Perhaps you should try some spelling variations:
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"
"modified df evaluation algorithm" » "modified df evolution algorithm", "modified df estimation algorithm", "modified df solution algorithm", "modified _ evaluation algorithm", "modified a valuation algorithm", "modified study evaluation algorithm", "modified adam evaluation algorithm", "modified bi1 evaluation algorithm"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified notion approximation algorithms") or ("modified df evaluation algorithm"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified notion approximation algorithms") OR ("modified df evaluation algorithm")).
• Removing quotes may allow a broader search: (( modified notion approximation algorithms ) or ( modified df evaluation algorithm )).
• Adding a wildcard symbol may retrieve word variants: (("modified notion approximation algorithms") or ("modified df evaluation algorithm"))*.