Perhaps you should try some spelling variations:
"modified network estimation algorithm" » "modified network optimization algorithm", "certified network estimation algorithm", "defined network estimation algorithm", "modified near estimation algorithm"
"modified invasive approximation algorithms" » "modified passive 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 invasive approximation algorithms") OR ("modified network estimation algorithm"))~.
• Removing quotes may allow a broader search: (( modified invasive approximation algorithms ) or ( modified network estimation algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified invasive approximation algorithms") or ("modified network estimation algorithm"))*.