Perhaps you should try some spelling variations:
"modified changing approximation algorithms" » "modified diophantine approximation algorithms", "modified caging approximation algorithms"
"modified network optimization algorithm" » "modified network optimization algorithms", "modified network optimisation algorithm", "modified network estimation algorithm", "certified network optimization algorithm", "defined network optimization algorithm", "modified near optimization 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: (("modified changing approximation algorithms") OR ("modified network optimization algorithm"))~.
• Removing quotes may allow a broader search: (( modified changing approximation algorithms ) or ( modified network optimization algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified changing approximation algorithms") or ("modified network optimization algorithm"))*.