Perhaps you should try some spelling variations:
"modified channel approximation algorithms" » "modified one approximation algorithms"
"modified parameters estimation algorithms" » "modified parameter estimation algorithms", "modified parameter estimates algorithms", "modified parameter optimization algorithms", "modified parameters estimation algorithm", "modified parameters optimization algorithms", "modified parameters optimisation algorithm"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified channel approximation algorithms") OR ("modified parameters estimation algorithms"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified channel approximation algorithms\") OR (\"modified parameters estimation algorithms\"))".
• Removing quotes may allow a broader search: (( modified channel approximation algorithms ) OR ( modified parameters estimation algorithms )).
• Adding a wildcard symbol may retrieve word variants: (("modified channel approximation algorithms") OR ("modified parameters estimation algorithms"))*.