Perhaps you should try some spelling variations:
estimation algorithms » estimation algorithm, optimization algorithms, optimisation algorithm
solution algorithm » evolution algorithm, convolution algorithms, evolutionary algorithm
modified positive » modified passive, modified adaptive
positive solution » positive solutions

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 _ estimation algorithms ) OR ( modified positive solution algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (( modified _ estimation algorithms ) or ( modified positive solution algorithm ))*.