Perhaps you should try some spelling variations:
"human sites periodicals." » "human fishes periodicals.", "human wastes periodicals.", "human crimes periodicals.", "human bites periodicals.", "human side periodicals.", "human stem periodicals."
"human gases periodicals." » "human games periodicals.", "human leases periodicals.", "human gas periodicals.", "human cases periodicals.", "human causes periodicals.", "human gamers periodicals."
"human states periodicals." » "human status periodicals.", "human state periodicals.", "human shapes 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 sites periodicals.") or ("human states periodicals."))) or ("human gases periodicals."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("human sites periodicals.") OR ("human states periodicals."))) OR ("human gases periodicals.")).
• Removing quotes may allow a broader search: (((( human sites periodicals. ) or ( human states periodicals. ))) or ( human gases periodicals. )).
• Adding a wildcard symbol may retrieve word variants: (((("human sites periodicals.") or ("human states periodicals."))) or ("human gases periodicals."))*.