Most laws have a provisions for the notification process and the timeline and must be followed to the letter of the law or can open up legal problems for you.
Here is some links to Ohio tenant/landlord links. There is definitely a process involved here.
Check with your local housing laws and your attorney.
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I would find a local real estate attorney and consult them.
Some of the questions they will ask:
Was there ever a lease or rental agreement?
How did they get there to start with?
What was the agreement regarding the occupancy?
What are the reasons for not wanting them there now?
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