N.D. Cent. Code § 15-39.2-06
In lieu of the election provided for by section 15-39.2-01, a college teacher may elect prior to July 1, 1980, notwithstanding the provisions of section 15-39.1-25, to receive benefits in accordance with chapter 15-39.1 and section 15-39.2-08. A teacher who elects to receive such benefits shall pay into the teachers' fund for retirement, in the manner provided for by section 15-39.2-07, the difference between the amount actually paid to the fund by the teacher during the period from July 1, 1969, to such time as the teacher exercises the election authorized by this section, and the amount which would have been required had the teacher's assessment rate remained the same as that of a public schoolteacher during that period. The amount must be determined by the board of trustees of the teachers' fund for retirement.
N.D.C.C. § 15-39.2-06