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