Perhaps you should try some spelling variations:
"human agents periodicals." » "human aspects periodicals.", "human arts periodicals.", "human plants periodicals.", "human agent periodicals.", "human agency periodicals."
"human gamers periodicals." » "human games periodicals.", "human cameras periodicals.", "human farmers periodicals.", "human gametes periodicals.", "human game periodicals.", "human cancers periodicals."
"human ages periodicals." » "human bees periodicals.", "human changes periodicals.", "human leases periodicals.", "human age periodicals.", "human images periodicals.", "human agent 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 gamers periodicals.") OR ((("human ages periodicals.") OR ("human agents periodicals."))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"human gamers periodicals.\") OR (((\"human ages periodicals.\") OR (\"human agents periodicals.\"))))".
• Removing quotes may allow a broader search: (( human gamers periodicals. ) OR ((( human ages periodicals. ) OR ( human agents periodicals. )))).
• Adding a wildcard symbol may retrieve word variants: (("human gamers periodicals.") OR ((("human ages periodicals.") OR ("human agents periodicals."))))*.