Perhaps you should try some spelling variations:
approximation algorithm » approximation algorithms
passive estimation » pose estimation
time approximation » one approximation, _ approximation
modified passive » modified adaptive
modified time » modified bi1, modified male

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( modified passive estimation algorithm ) or ( modified time approximation algorithm ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( modified passive estimation algorithm ) OR ( modified time approximation algorithm )).
• Adding a wildcard symbol may retrieve word variants: (( modified passive estimation algorithm ) or ( modified time approximation algorithm ))*.