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