Perhaps you should try some spelling variations:
"modified coverage approximation algorithms" » "modified average approximation algorithms"
"modified large variation algorithms" » "modified large estimation algorithms", "modified large vision algorithms", "modified large estimation algorithm", "modified large evaluation algorithms", "modified male variation 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 coverage approximation algorithms") or ("modified large variation algorithms"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified coverage approximation algorithms") OR ("modified large variation algorithms")).
• Removing quotes may allow a broader search: (( modified coverage approximation algorithms ) or ( modified large variation algorithms )).
• Adding a wildcard symbol may retrieve word variants: (("modified coverage approximation algorithms") or ("modified large variation algorithms"))*.