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

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