Perhaps you should try some spelling variations:
"varying environments and operational considerations" » "varying environments and additional considerations", "varying environment and operational considerations", "working environments and operational considerations", "changing environments and operational considerations"
"learning environments and operational considerations" » "learning environments and additional considerations"
"varying environments and operational definitions" » "varying environments and operational definition", "varying environments and operational decision", "varying environment and operational definitions", "working environments and operational definitions", "changing environments and operational definitions"

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 environments and operational definitions") OR ((("varying environments and operational considerations") OR ("learning environments and operational considerations")))).
• Removing quotes may allow a broader search: (( varying environments and operational definitions ) or ((( varying environments and operational considerations ) or ( learning environments and operational considerations )))).
• Adding a wildcard symbol may retrieve word variants: (("varying environments and operational definitions") or ((("varying environments and operational considerations") or ("learning environments and operational considerations"))))*.