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