Perhaps you should try some spelling variations:
"defined network optimization algorithms" » "defined network optimisation algorithm", "defined network estimation algorithms", "defined network estimation algorithm"
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified notion approximation algorithms") OR ("defined network optimization algorithms"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified notion approximation algorithms\") OR (\"defined network optimization algorithms\"))*".
• Removing quotes may allow a broader search: (( modified notion approximation algorithms ) OR ( defined network optimization algorithms ))*.