Perhaps you should try some spelling variations:
"modified multiobjective approximation algorithms" » "modified multiobjective optimization algorithms"
"modified chuon estimation algorithm" » "modified channel estimation algorithm", "modified motion estimation algorithm", "modified carbon estimation algorithm"

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 approximation algorithms") OR ("modified chuon estimation algorithm"))~.
• Removing quotes may allow a broader search: (( modified multiobjective approximation algorithms ) or ( modified chuon estimation algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified multiobjective approximation algorithms") or ("modified chuon estimation algorithm"))*.