Perhaps you should try some spelling variations:
estimation algorithms » optimization algorithms, optimisation algorithm, approximation algorithms
objective estimation » objective optimization, objective allocation
learning estimation » learning emotion, lighting estimation
modified learning » mobile learning, modified caging

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

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