Perhaps you should try some spelling variations:
covid environment » cold environment, closed environment, cloud environment
oecd environment » oecd environmental, field environment, grid environment
policy papers » policy paper

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 (covid environment)) ((policy papers) OR (policy part)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((oecd environment) or (covid environment)) ((policy papers) OR (policy part))".
• Adding a wildcard symbol may retrieve word variants: ((oecd environment) or (covid environment)) ((policy papers) OR (policy part))*.