Okla. Stat. tit. 58, § 287

The inventory must be signed by the appraisers, and the executor or administrator must take and subscribe an oath, before an officer authorized to administer oaths, that the inventory contains a true statement of all the estate of the decedent which has come to his knowledge and possession, and particularly of all money belonging to the decedent, and of all just claims of the decedent against the affiant. The oath must be endorsed upon or annexed to the inventory.