Perhaps you should try some spelling variations:
"modified multiobjective optimization algorithms" » "modified multiobjective optimisation algorithm", "modified multiobjective estimation algorithm", "modified multiobjective optimized algorithms"
"modified _ estimation algorithms" » "modified _ estimation algorithm", "modified _ optimisation algorithm", "modified _ 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 multiobjective optimization algorithms") OR ("modified _ estimation algorithms"))~.
• Removing quotes may allow a broader search: (( modified multiobjective optimization algorithms ) or ( modified _ estimation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified multiobjective optimization algorithms") or ("modified _ estimation algorithms"))*.