Perhaps you should try some spelling variations:
"unmanned arterial vehicle" » "unmanned arial vehicle", "skinned arterial vehicle", "unmanned area vehicle", "unmanned aerial vehicle", "unmanned lateral vehicle", "unmanned criteria vehicle"
"damaged arterial vehicle" » "damaged aerial vehicle", "damaged lateral vehicle", "damaged criteria vehicle", "damaged bacterial vehicle", "damaged material vehicle", "damaged materials vehicle"

Try widening your search to All Fields.

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: (((("unmanned arterial vehicle") OR ("damaged arterial vehicle"))) OR ("unmanned aerial vehicles")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"unmanned arterial vehicle\") OR (\"damaged arterial vehicle\"))) or (\"unmanned aerial vehicles\"))".
• Removing quotes may allow a broader search: (((( unmanned arterial vehicle ) OR ( damaged arterial vehicle ))) or ( unmanned aerial vehicles )).
• Adding a wildcard symbol may retrieve word variants: (((("unmanned arterial vehicle") OR ("damaged arterial vehicle"))) or ("unmanned aerial vehicles"))*.