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