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

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified multiobjective estimation algorithms\") OR (\"modified sphere optimized algorithms\"))~".
• Removing quotes may allow a broader search: (( modified multiobjective estimation algorithms ) OR ( modified sphere optimized algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified multiobjective estimation algorithms") OR ("modified sphere optimized algorithms"))*.