Perhaps you should try some spelling variations:
mitigation techniques » imputation techniques
reduction techniques » reduction technique, imputation techniques
ko2 mitigation » _ mitigation, error mitigation
n reduction » _ reduction, _ prediction, _ production
based ko2 » based no2, based co, based k
based n » based _, based k, based no2

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( learning-based n reduction techniques ) OR ( learning-based ko2 mitigation techniques ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( learning-based n reduction techniques ) OR ( learning-based ko2 mitigation techniques ))".
• Adding a wildcard symbol may retrieve word variants: (( learning-based n reduction techniques ) OR ( learning-based ko2 mitigation techniques ))*.