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