Perhaps you should try some spelling variations:
"modified stochastic optimization algorithms" » "modified stochastic optimisation algorithm", "modified stochastic estimation algorithms", "modified stochastic estimation algorithm"
"modified passive approximation algorithms" » "modified time approximation algorithms", "modified adaptive approximation algorithms"

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified passive approximation algorithms\") OR (\"modified stochastic optimization algorithms\"))~".
• Removing quotes may allow a broader search: (( modified passive approximation algorithms ) OR ( modified stochastic optimization algorithms ))~.
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