Perhaps you should try some spelling variations:
"defined network approximation algorithm" » "defined network approximation algorithms", "designed network approximation algorithm"
"modified network optimization algorithms" » "modified network optimisation algorithm", "modified network estimation algorithms", "modified network estimation algorithm", "certified network optimization algorithms", "modified near optimization algorithms"

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