Perhaps you should try some spelling variations:
approximation algorithm » approximation algorithms
optimization algorithms » optimisation algorithm, estimation algorithms, estimation algorithm
market approximation » one approximation, time approximation
market optimization » game optimization, parameter optimization, market capitalization

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

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