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