Perhaps you should try some spelling variations:
"modified a validation algorithm" » "modified a estimation algorithm", "modified a predation algorithm", "modified a estimation algorithms", "modified _ validation algorithm", "modified a valuation algorithm", "modified _ validating algorithm", "modified df validation algorithm", "modified adam validation algorithm"
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified a validation algorithm\") OR (\"modified notion approximation algorithms\"))~".
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