Perhaps you should try some spelling variations:
lunar reference » author reference, shear references
step reference » step references, steps references, steam reference
d collections » 6 collections, 5 collections, 7 collections
_ collections » _ collection, _ collecting, _ collective

Try widening your search to All Fields.

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: (("((lunar reference) or (step reference)) collection") OR ("((lunar reference) or (step reference))((d collections) or (_ collections))")).
• Removing quotes may allow a broader search: (( ((lunar reference) or (step reference)) collection ) or ( ((lunar reference) or (step reference))((d collections) or (_ collections)) )).
• Adding a wildcard symbol may retrieve word variants: (("((lunar reference) or (step reference)) collection") or ("((lunar reference) or (step reference))((d collections) or (_ collections))"))*.