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