Perhaps you should try some spelling variations:
"modified adaptive approximation algorithms" » "modified time approximation algorithms", "modified passive approximation algorithms"
"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.

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified adaptive approximation algorithms") or ("modified parameter estimates algorithms"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified adaptive approximation algorithms") OR ("modified parameter estimates algorithms")).
• Removing quotes may allow a broader search: (( modified adaptive approximation algorithms ) or ( modified parameter estimates algorithms )).
• Adding a wildcard symbol may retrieve word variants: (("modified adaptive approximation algorithms") or ("modified parameter estimates algorithms"))*.