Perhaps you should try some spelling variations:
"modified time approximation algorithms" » "modified one approximation algorithms", "modified _ approximation algorithms", "modified bi1 approximation algorithms", "modified male approximation algorithms"
"modified learning method algorithm" » "mobile learning method algorithm", "modified caging method algorithm", "modified learning mom algorithm", "modified learning methods algorithm", "modified graining methods algorithm", "modified learning emotion 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 time approximation algorithms") or ("modified learning method algorithm"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified time approximation algorithms") OR ("modified learning method algorithm")).
• Removing quotes may allow a broader search: (( modified time approximation algorithms ) or ( modified learning method algorithm )).
• Adding a wildcard symbol may retrieve word variants: (("modified time approximation algorithms") or ("modified learning method algorithm"))*.