Perhaps you should try some spelling variations:
"modified multiobjective approximation algorithms" » "modified multiobjective optimization algorithms"
"machines using search algorithm" » "machines using source algorithm", "machinery using search algorithm", "machines using egarch algorithm", "machines nursing research algorithm", "machines using servo algorithm"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("machines using search algorithm") OR ("modified multiobjective approximation algorithms"))~.
• Removing quotes may allow a broader search: (( machines using search algorithm ) or ( modified multiobjective approximation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("machines using search algorithm") or ("modified multiobjective approximation algorithms"))*.