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