Perhaps you should try some spelling variations:
"modified coverage approximation algorithms" » "modified average approximation algorithms"
"modified image classification algorithm" » "modified disease classification algorithm", "modified binary classification algorithm", "modified _ classification algorithm", "modified male classification 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 coverage approximation algorithms") OR ("modified image classification algorithm"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified coverage approximation algorithms\") OR (\"modified image classification algorithm\"))".
• Removing quotes may allow a broader search: (( modified coverage approximation algorithms ) OR ( modified image classification algorithm )).
• Adding a wildcard symbol may retrieve word variants: (("modified coverage approximation algorithms") OR ("modified image classification algorithm"))*.