Perhaps you should try some spelling variations:
"modified aging approximation algorithms" » "modified one approximation algorithms", "modified time approximation algorithms", "modified average approximation algorithms", "modified caging approximation algorithms"
"modified network estimation algorithm" » "modified network optimization algorithm", "certified network estimation algorithm", "defined network estimation algorithm", "modified near estimation algorithm"

Try widening your search to All Fields.

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

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