Perhaps you should try some spelling variations:
"modified multiobjective estimation algorithm" » "modified multiobjective optimization algorithm"
"modified sphere optimisation algorithm" » "modified sphere optimization algorithms", "modified sphere estimation algorithms", "modified sphere estimation algorithm"

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• Performing a fuzzy search may retrieve terms with similar spellings: (("modified multiobjective estimation algorithm") OR ("modified sphere optimisation algorithm"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified multiobjective estimation algorithm\") OR (\"modified sphere optimisation algorithm\"))*".
• Removing quotes may allow a broader search: (( modified multiobjective estimation algorithm ) OR ( modified sphere optimisation algorithm ))*.