Perhaps you should try some spelling variations:
estimation algorithms » optimization algorithms, optimisation algorithm, approximation algorithms
parameters estimation » parameter estimation, parameter estimates, parameter optimization
passive estimation » pose estimation
modified passive » modified adaptive

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