Perhaps you should try some spelling variations:
estimation algorithms » estimation algorithm, optimization algorithms, optimisation algorithm
invasive estimation » invasive ventilation
one approximation » time approximation, _ approximation, rough approximations
modified invasive » modified passive
modified one » modified male, modified near, modified orca

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 one approximation algorithms ) OR ( modified invasive estimation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (( modified one approximation algorithms ) or ( modified invasive estimation algorithms ))*.