Perhaps you should try some spelling variations:
"modified df approximation algorithm" » "modified df approximation algorithms", "modified _ approximation algorithm", "modified one approximation algorithm", "modified time approximation algorithm", "modified adam approximation algorithm", "modified bi1 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.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified df approximation algorithm\") OR (\"modified network optimization algorithm\"))~".
• Removing quotes may allow a broader search: (( modified df approximation algorithm ) OR ( modified network optimization algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified df approximation algorithm") OR ("modified network optimization algorithm"))*.