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

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

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