Perhaps you should try some spelling variations:
"modified bi1 approximation algorithm" » "modified bi1 approximation algorithms", "modified time approximation algorithm", "modified _ approximation algorithm", "modified one approximation algorithm"
"modified network optimization algorithm" » "modified network optimization algorithms", "modified network optimisation algorithm", "modified network estimation algorithm", "certified network optimization algorithm", "defined network optimization algorithm", "modified near optimization 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: (("modified bi1 approximation algorithm") OR ("modified network optimization algorithm"))~.
• Removing quotes may allow a broader search: (( modified bi1 approximation algorithm ) or ( modified network optimization algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified bi1 approximation algorithm") or ("modified network optimization algorithm"))*.