Perhaps you should try some spelling variations:
"modified df approximation algorithm" » "modified df approximation algorithms", "modified _ approximation algorithm", "modified one approximation algorithm", "modified time approximation algorithm", "modified adam approximation algorithm", "modified bi1 approximation algorithm"
"modified stochastic estimation algorithms" » "modified stochastic optimization algorithms", "modified stochastic estimation algorithm", "modified stochastic optimisation 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 df approximation algorithm") OR ("modified stochastic estimation algorithms"))~.
• Removing quotes may allow a broader search: (( modified df approximation algorithm ) or ( modified stochastic estimation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified df approximation algorithm") or ("modified stochastic estimation algorithms"))*.