Perhaps you should try some spelling variations:
learning environmental » learning environments, learning environment, planning environmental
operational conditions » operational considerations, operational definitions, operational control
operating conditions » working conditions
varying environment » learning environment, working environment, making environment

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: ((varying environment) OR (learning environmental)) AND ((operational conditions) OR (operating conditions)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((varying environment) or (learning environmental)) and ((operational conditions) OR (operating conditions))".
• Adding a wildcard symbol may retrieve word variants: ((varying environment) or (learning environmental)) and ((operational conditions) OR (operating conditions))*.