Perhaps you should try some spelling variations:
field environment » food environment, world environment, wind environment
covid environment » cold environment, closed environment, cloud environment
policy papers » policy paper, policy part

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: ((field environment) OR (covid environment)) policy papers.
• Adding a wildcard symbol may retrieve word variants: ((field environment) or (covid environment)) policy papers*.