Perhaps you should try some spelling variations:
"modified df approximation algorithms" » "modified _ approximation algorithms", "modified one approximation algorithms", "modified time approximation algorithms", "modified adam approximation algorithms", "modified bi1 approximation algorithms"
"modified dfdamdamdaptive estimation algorithm" » "modified _damdamdaptive estimation algorithm", "modified adamdamdamdaptive estimation algorithm", "modified bi1damdamdaptive estimation algorithm"

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 dfdamdamdaptive estimation algorithm") OR ("modified df approximation algorithms"))~.
• Removing quotes may allow a broader search: (( modified dfdamdamdaptive estimation algorithm ) or ( modified df approximation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified dfdamdamdaptive estimation algorithm") or ("modified df approximation algorithms"))*.