Perhaps you should try some spelling variations:
optimisation algorithm » optimization algorithms, estimation algorithm, estimation algorithms
risk approximation » _ approximation, one approximation, rough approximations
time approximation » one approximation, _ approximation
risk optimisation » _ optimisation, risk estimation

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: (( risk optimisation algorithm ) OR ( ((risk approximation) OR (time approximation)) algorithms ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( risk optimisation algorithm ) or ( ((risk approximation) OR (time approximation)) algorithms ))~".
• Adding a wildcard symbol may retrieve word variants: (( risk optimisation algorithm ) or ( ((risk approximation) OR (time approximation)) algorithms ))*.