Perhaps you should try some spelling variations:
validation algorithm » estimation algorithm, predation algorithm, estimation algorithms
one approximation » time approximation, _ approximation, rough approximations
modified one » modified male, modified near, modified orca
a validation » _ validation, a valuation, _ validating
modified a » modified _, modified df, modified adam

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

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