Okla. Stat. tit. 12, § 12-617
Reference in vacation
A judge, in vacation, upon the written consent of the parties,
may make an order of reference which the court of which he is a
member could make in term time. In such case, the order of
reference shall be made on the written agreement of the parties to
refer, and shall be filed with the clerk of the court, with the
other papers in the case.
R.L. 1910, § 5023.