Perhaps you should try some spelling variations:
optimisation algorithm » optimization algorithms, estimation algorithms
staffing optimisation » staffing optimization, static optimization
invasive estimation » invasive ventilation
modified invasive » modified passive
modified staffing » modified caging

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( modified invasive estimation algorithm ) OR ( modified staffing optimisation algorithm ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( modified invasive estimation algorithm ) OR ( modified staffing optimisation algorithm ))".
• Adding a wildcard symbol may retrieve word variants: (( modified invasive estimation algorithm ) OR ( modified staffing optimisation algorithm ))*.