Perhaps you should try some spelling variations:
"modified oxygen convolution algorithms" » "modified oxygen evolution algorithm", "modified oxygen solution algorithm", "modified oxygen evolution algorithms"
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"

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 notion approximation algorithms") OR ("modified oxygen convolution algorithms"))~.
• Removing quotes may allow a broader search: (( modified notion approximation algorithms ) or ( modified oxygen convolution algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified notion approximation algorithms") or ("modified oxygen convolution algorithms"))*.