Perhaps you should try some spelling variations:
estimation algorithms » estimation algorithm, optimization algorithms, optimisation algorithm
invasive estimation » invasive ventilation
modified learning » mobile learning, modified caging
modified invasive » modified passive
method algorithm » mom algorithm
learning method » learning methods, graining methods, learning emotion

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