Perhaps you should try some spelling variations:
approximation algorithm » approximation algorithms
response approximation » one approximation, response association
estimation algorithms » estimation algorithm, optimization algorithms, optimisation algorithm
qoe estimation » pose estimation, _ estimation, cover estimations

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: (( response approximation algorithm ) OR ( qoe estimation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (( response approximation algorithm ) or ( qoe estimation algorithms ))*.