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

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( ((post approximation) OR (one approximation)) algorithms ) or ( risk optimisation algorithm ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( ((post approximation) OR (one approximation)) algorithms ) OR ( risk optimisation algorithm ))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ((post approximation) OR (one approximation)) algorithms ) or ( risk optimisation algorithm ))*".