Perhaps you should try some spelling variations:
"modified allocation approximation algorithms" » "modified allocation optimization algorithms"
"modified topology estimation algorithms" » "modified topology estimation algorithm", "modified topology optimization algorithms", "modified topology optimisation algorithm"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified topology estimation algorithms") or ("modified allocation approximation algorithms"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified topology estimation algorithms") OR ("modified allocation approximation algorithms")).
• Removing quotes may allow a broader search: (( modified topology estimation algorithms ) or ( modified allocation approximation algorithms )).
• Adding a wildcard symbol may retrieve word variants: (("modified topology estimation algorithms") or ("modified allocation approximation algorithms"))*.