Perhaps you should try some spelling variations:
"modified coverage approximation algorithms" » "modified average approximation algorithms"
"modified invasive ventilation algorithm" » "modified invasive estimation algorithm", "modified invasive estimation algorithms", "modified invasive evolution algorithm", "modified adaptive ventilation algorithm", "modified passive ventilation 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 invasive ventilation algorithm") OR ("modified coverage approximation algorithms"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified invasive ventilation algorithm\") OR (\"modified coverage approximation algorithms\"))*".
• Removing quotes may allow a broader search: (( modified invasive ventilation algorithm ) OR ( modified coverage approximation algorithms ))*.