Perhaps you should try some spelling variations:
"modified oxygen estimation algorithms" » "modified oxygen estimation algorithm", "modified oxygen optimization algorithms", "modified oxygen optimisation algorithm", "modified oxygen saturation algorithms"
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"

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• Performing a fuzzy search may retrieve terms with similar spellings: (("modified oxygen estimation algorithms") or ("modified notion approximation algorithms"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified oxygen estimation algorithms") OR ("modified notion approximation algorithms"))*.
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