Perhaps you should try some spelling variations:
"nato science overview a:, life sciences" » "nato science review a:, life sciences", "nato service overview a:, life sciences", "nato change overview a:, life sciences", "national science overview a:, life sciences"
"nato science service a:, life sciences" » "national science service a:, life sciences"

Try widening your search to All Fields.

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• If you are trying to use Boolean operators, they must be ALL CAPS: (("nato science overview a:, life sciences") OR ((("nato science service a:, life sciences") OR ("radio science service a:, life sciences")))).
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• Removing quotes may allow a broader search: (( nato science overview a:, life sciences ) or ((( nato science service a:, life sciences ) OR ( radio science service a:, life sciences )))).
• Adding a wildcard symbol may retrieve word variants: (("nato science overview a:, life sciences") or ((("nato science service a:, life sciences") OR ("radio science service a:, life sciences"))))*.