Perhaps you should try some spelling variations:
"modified multiobjective approximation algorithms" » "modified multiobjective optimization algorithms"
"modified robust estimation algorithm" » "modified robust optimization algorithm", "modified pose estimation algorithm", "modified risk estimation algorithm"

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified multiobjective approximation algorithms") or ("modified robust estimation algorithm"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified multiobjective approximation algorithms") OR ("modified robust estimation algorithm")).
• Removing quotes may allow a broader search: (( modified multiobjective approximation algorithms ) or ( modified robust estimation algorithm )).
• Adding a wildcard symbol may retrieve word variants: (("modified multiobjective approximation algorithms") or ("modified robust estimation algorithm"))*.