Perhaps you should try some spelling variations:
"bvocal emissions" » "vocal emissions", "bvoc emissions", "bvocs emissions"
"dioxide emission" » "dioxide emissions", "oxide emissions"
"voc emissions" » "bvoc emissions", "voc emission", "vocal emissions"

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: (((("voc emissions") OR ("bvocal emissions"))) OR ("dioxide emission")).
• Removing quotes may allow a broader search: (((( voc emissions ) or ( bvocal emissions ))) or ( dioxide emission )).
• Adding a wildcard symbol may retrieve word variants: (((("voc emissions") or ("bvocal emissions"))) or ("dioxide emission"))*.