Kernrechtsfrage
Whether the lease termination of 21 January 2005 became void because the tenants accepted the proposed amendment by returning the signed addendum.
Extrahierter Entscheid
The addendum was not proven to have been returned; no meeting of wills occurred, so the offered amendment was not concluded and the termination remained effective.
Extrahierte Begründung
Under Art. 8 CC, the tenants bore the burden of proving return of the signed addendum. They provided no direct proof, and the absence of later reference to the document did not make the fact established; the appellate court was not arbitrary in rejecting that inference.