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