Perhaps you should try some spelling variations:
"human cases periodicals." » "human caves periodicals.", "human classes periodicals.", "human leases periodicals.", "human causes periodicals.", "human case periodicals.", "human caspases periodicals."
"human gases periodicals." » "human games periodicals.", "human leases periodicals.", "human gas periodicals.", "human causes 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."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("human bees periodicals.") or ((("human gases periodicals.") OR ("human cases periodicals."))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("human bees periodicals.") OR ((("human gases periodicals.") OR ("human cases periodicals.")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"human bees periodicals.\") or (((\"human gases periodicals.\") OR (\"human cases periodicals.\"))))".
• Removing quotes may allow a broader search: (( human bees periodicals. ) or ((( human gases periodicals. ) OR ( human cases periodicals. )))).
• Adding a wildcard symbol may retrieve word variants: (("human bees periodicals.") or ((("human gases periodicals.") OR ("human cases periodicals."))))*.