Nevada constitution
Article 4: legislative department
Section 5

It shall be the mandatory duty of the Legislature at its first session after the taking of the decennial census of the United States in the year 1950, and after each subsequent decennial census, to fix by law the number of Senators and Assemblymen, and apportion them among the several counties of the State, or among legislative districts which may be established by law, according to the number of inhabitants in them, respectively.