Perhaps you should try some spelling variations:
optimization algorithms » optimisation algorithm, estimation algorithms, estimation algorithm
qoe approximation » time approximation, _ approximation, rough approximations
one approximation » time approximation, _ approximation, rough approximations
qoe optimization » game optimization, _ optimization, stage optimization

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( ((qoe approximation) OR (one approximation)) algorithms ) or ( qoe optimization algorithms ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( ((qoe approximation) OR (one approximation)) algorithms ) OR ( qoe optimization algorithms )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ((qoe approximation) OR (one approximation)) algorithms ) or ( qoe optimization algorithms ))".
• Adding a wildcard symbol may retrieve word variants: (( ((qoe approximation) OR (one approximation)) algorithms ) or ( qoe optimization algorithms ))*.