A.R.S. § 6-1007

Neither the death nor incompetency of a lessee revokes the authority of a lessor to deal with an agent who has been authorized in writing by such lessee until the lessor has actual knowledge of the fact of death or of an adjudication of incompetency of the lessee, nor is the revocation of authority of such agent effective as to the lessor until the lessor receives written notice of the revocation signed by the individual lessee who granted the authority or, in the case of a corporation, partnership or association, evidence satisfactory to the lessor of such revocation.