Perhaps you should try some spelling variations:
"modified multiobjective approximation algorithms" » "modified multiobjective optimization algorithms"
"modified model estimation algorithm" » "modified pose estimation algorithm", "modified cover estimations algorithm", "modified motion estimation algorithm", "modified male 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 model estimation algorithm") OR ("modified multiobjective approximation algorithms"))~.
• Removing quotes may allow a broader search: (( modified model estimation algorithm ) or ( modified multiobjective approximation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified model estimation algorithm") or ("modified multiobjective approximation algorithms"))*.