Ok. Const. art. XXIII, § 4
OK Const., Article XXIII, Section 4
Employment underground - Hours of labor underground. Boys and girls under the age of eighteen years shall not be employed, underground, in the operation of mines; and, except in cases of emergency, eight hours shall constitute a day's work underground in all mines in the State. Amended by State Question No. 589, Legislative Referendum No. 253, adopted at election held on Nov. 4, 1986. Amendment proposed by Laws 1985, p. 1666, S.J.R. No. 16, § 1.