Perhaps you should try some spelling variations:
"key regulators perspectives" » "key regulators perspective", "key regulations perspectives", "key regulatory perspective", "key regulator perspectives", "_ regulators perspectives"
"a regulatory perspectives" » "a regulatory perspective", "a regulatory peptides"
"a regulatory properties" » "a regularity properties", "a regular properties", "a regulatory proteins"

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: (("key regulators perspectives") OR ((("a regulatory properties") OR ("a regulatory perspectives"))))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"key regulators perspectives\") or (((\"a regulatory properties\") OR (\"a regulatory perspectives\"))))*".
• Removing quotes may allow a broader search: (( key regulators perspectives ) or ((( a regulatory properties ) OR ( a regulatory perspectives ))))*.