Perhaps you should try some spelling variations:
"modified coverage approximation algorithms" » "modified average approximation algorithms"
"modified level evolution algorithm" » "modified level solution algorithm", "modified level evolutionary algorithm", "modified level convolution algorithms", "modified legal revolution algorithm", "modified global evolution algorithm", "modified level production algorithm"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified coverage approximation algorithms") OR ("modified level evolution algorithm"))~.
• Removing quotes may allow a broader search: (( modified coverage approximation algorithms ) or ( modified level evolution algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified coverage approximation algorithms") or ("modified level evolution algorithm"))*.