(1) A referendum group, as referred to in sections 68-621 to 68-630, shall consist of the employees of the state, a single political subdivision of this state, or any instrumentality jointly created by this state and any other state or states, the employees of which are or may be members of a retirement system covering such employees, except that: (a) The employees of the University of Nebraska shall constitute a referendum group; (b) the employees of a Class V school district shall constitute a referendum group; (c) all employees of the State of Nebraska who are or may be members of the School Employees Retirement System of the State of Nebraska, including employees of institutions operated by the Board of Trustees of the Nebraska State Colleges, employees of institutions operated by the Department of Correctional Services and the Department of Health and Human Services, and employees subordinate to the State Board of Education, shall constitute a referendum group; and (d) all employees of school districts of the State of Nebraska, county superintendents, and county school administrators, who are or may be members of the School Employees Retirement System of the State of Nebraska, shall constitute a single referendum group.

(2) The managing authority of a political subdivision or educational institution shall be the board, committee, or council having general authority over a political subdivision, university, college, or school district whose employees constitute or are included in a referendum group; the managing authority of the state shall be the Governor; and insofar as sections 68-601 to 68-631 may be applicable to county superintendents and county school administrators, managing authority shall mean the board of county commissioners or county supervisors of the county in which the county superintendent was elected or with which the county school administrator contracted.

(3) Eligible employees, as referred to in sections 68-621 to 68-630, shall mean those employees of the state or any political subdivision thereof who at or during the time of voting in a referendum as herein provided are in positions covered by a retirement system, are members of such retirement system, and were in such positions at the time of giving of the notice of such referendum, as herein required, except that no such employee shall be considered an eligible employee if at the time of such voting such employee is in a position to which the state agreement applies or if such employee is in service in a police officer or firefighter position.

(4) State agreement, as referred to in sections 68-621 to 68-630, shall mean the agreement between the State of Nebraska and the designated officer of the United States of America entered into pursuant to section 68-603.