Perhaps you should try some spelling variations:
"modified cover optimization algorithms" » "modified cover optimisation algorithm", "modified cover estimation algorithms", "modified cover estimation algorithm", "modified qoe optimization algorithms", "modified game optimization algorithms"
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"

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 cover optimization algorithms") OR ("modified notion approximation algorithms"))~.
• Removing quotes may allow a broader search: (( modified cover optimization algorithms ) or ( modified notion approximation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified cover optimization algorithms") or ("modified notion approximation algorithms"))*.