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 parameter estimates algorithms" » "modified parameter estimation algorithms", "modified parameter estimation algorithm", "modified parameter optimized algorithms"

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified df approximation algorithm\") OR (\"modified parameter estimates algorithms\"))~".
• Removing quotes may allow a broader search: (( modified df approximation algorithm ) OR ( modified parameter estimates algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified df approximation algorithm") OR ("modified parameter estimates algorithms"))*.