Ohio Rev. Code § 1331.10: Evidence.

In prosecutions under sections 1331.01 to 1331.14 of the Revised Code, it is sufficient to prove that a trust or combination exists, and that the defendant belonged to it, or acted for or in connection with it, without proving all the members belonging to it, or proving or producing an article of agreement, or a written instrument on which it may have been based; or that it was evidenced by a written instrument.