Perhaps you should try some spelling variations:
"modified coverage approximation algorithms" » "modified average approximation algorithms", "modified _verage approximation algorithms", "modified dfverage approximation algorithms", "modified orcaverage approximation algorithms"
"modified co evolutionary algorithm" » "modified co evolution algorithm", "modified co solution algorithm", "modified _ evolutionary algorithm", "modified df evolutionary algorithm", "modified orca evolutionary algorithm"

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