Perhaps you should try some spelling variations:
"modified df approximation algorithm" » "modified df approximation algorithms", "modified _ approximation algorithm", "modified one approximation algorithm", "modified time approximation algorithm", "modified adam approximation algorithm", "modified bi1 approximation algorithm"
"modified allocation estimation algorithms" » "modified allocation optimization algorithms", "modified motion estimation algorithms", "modified allocation estimation algorithm", "modified allocation optimisation algorithm"

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

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