Perhaps you should try some spelling variations:
"modified coverage approximation algorithms" » "modified average approximation algorithms"
"modified objective estimation algorithms" » "modified objective estimation algorithm", "modified objective optimization algorithms", "modified objective optimisation algorithm", "modified objective allocation algorithms"

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

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