Perhaps you should try some spelling variations:
closed environment » cloud environment, crowded environment, cloud environments
oecd environment » oecd environmental, field environment, covid environment
policy papers » policy part
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: ((oecd environment) OR (closed environment)) ((policy papers) OR (policy paper)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((oecd environment) or (closed environment)) ((policy papers) OR (policy paper))".
• Adding a wildcard symbol may retrieve word variants: ((oecd environment) or (closed environment)) ((policy papers) OR (policy paper))*.