Perhaps you should try some spelling variations:
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"national science services c:, mathematical and physical sciences" » "national science service c:, mathematical and physical sciences", "national science overview c:, mathematical and physical sciences", "national voice services c:, mathematical and physical sciences", "natural science services c:, mathematical and physical sciences", "spatial science services c:, mathematical and physical sciences", "animal science services c:, mathematical and physical sciences", "national science services case:, mathematical and physical sciences"

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• If you are trying to use Boolean operators, they must be ALL CAPS: (((("nato science services c:, mathematical and medical sciences") OR ("nato science services ch:, mathematical and medical sciences"))) OR ("national science services c:, mathematical and physical sciences")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"nato science services c:, mathematical and medical sciences\") OR (\"nato science services ch:, mathematical and medical sciences\"))) or (\"national science services c:, mathematical and physical sciences\"))".
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• Adding a wildcard symbol may retrieve word variants: (((("nato science services c:, mathematical and medical sciences") OR ("nato science services ch:, mathematical and medical sciences"))) or ("national science services c:, mathematical and physical sciences"))*.