Perhaps you should try some spelling variations:
"nato science theories a:, life sciences" » "nato science three a:, life sciences", "radio science theories a:, life sciences", "national science theories a:, life sciences"
"natural science theories a:, life sciences" » "natural science three a:, life sciences", "natural sciences theories a:, life sciences"
"natural science theory a:, life sciences" » "natural sciences theory a:, life sciences"

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: (("nato science theories a:, life sciences") OR ((("natural science theories a:, life sciences") OR ("natural science theory a:, life sciences")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"nato science theories a:, life sciences\") or (((\"natural science theories a:, life sciences\") OR (\"natural science theory a:, life sciences\"))))".
• Removing quotes may allow a broader search: (( nato science theories a:, life sciences ) or ((( natural science theories a:, life sciences ) OR ( natural science theory a:, life sciences )))).
• Adding a wildcard symbol may retrieve word variants: (("nato science theories a:, life sciences") or ((("natural science theories a:, life sciences") OR ("natural science theory a:, life sciences"))))*.