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

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