Perhaps you should try some spelling variations:
optimization algorithms » optimisation algorithm, estimation algorithms, estimation algorithm
approximation algorithm » approximation algorithms
df approximation » _ approximation, one approximation, time approximation
qoe optimization » game optimization, _ optimization, stage optimization
modified qoe » modified male, modified _, modified bi1
modified df » modified _, modified adam, modified bi1

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