Perhaps you should try some spelling variations:
"the frontier functions" » "the wannier functions"
"the frontier section" » "the frontiers section", "the frontier region", "the frontal sections"
"the frontier second" » "the frontiers section"

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: (((("the frontier section") OR ("the frontier functions"))) OR ("the frontier second")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"the frontier section\") OR (\"the frontier functions\"))) or (\"the frontier second\"))".
• Removing quotes may allow a broader search: (((( the frontier section ) OR ( the frontier functions ))) or ( the frontier second )).
• Adding a wildcard symbol may retrieve word variants: (((("the frontier section") OR ("the frontier functions"))) or ("the frontier second"))*.