Perhaps you should try some spelling variations:
"human causes periodicals." » "human cases periodicals.", "human classes periodicals.", "human courses periodicals.", "human cancers periodicals.", "human viruses periodicals.", "human cancer periodicals."
"human gases periodicals." » "human games periodicals.", "human leases periodicals.", "human gas periodicals.", "human cases periodicals.", "human gamers periodicals.", "human based periodicals."
"human bees periodicals." » "human diabetes periodicals.", "human indexes periodicals.", "human devices periodicals.", "human bites periodicals.", "human beast periodicals.", "human bones periodicals."

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("human bees periodicals.") or ((("human gases periodicals.") OR ("human causes periodicals."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("human bees periodicals.") OR ((("human gases periodicals.") OR ("human causes periodicals.")))).
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• Adding a wildcard symbol may retrieve word variants: (("human bees periodicals.") or ((("human gases periodicals.") OR ("human causes periodicals."))))*.