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