Perhaps you should try some spelling variations:
"negative spread" » "vegetative spread", "negative strand", "negative real"
"negative tread" » "negative trends", "negative real", "negative head"
"negative areas" » "negative breast", "negative real", "relative areas"

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: (((("negative tread") OR ("negative areas"))) OR ("negative spread")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"negative tread\") OR (\"negative areas\"))) or (\"negative spread\"))".
• Removing quotes may allow a broader search: (((( negative tread ) OR ( negative areas ))) or ( negative spread )).
• Adding a wildcard symbol may retrieve word variants: (((("negative tread") OR ("negative areas"))) or ("negative spread"))*.