Sweden - 1974 Constitution

Part The Instrument of Government
Title Article 1
Chapter 3 - The Riksdag
Article

1

The Riksdag shall be appointed by means of free, secret and direct elections. In such elections, votes shall be cast for parties, with an option for the voter to express a preference for a particular candidate. [...]

Categories - Electoral party (Electoral rules/formula)
Source Gisbert H. Flanz ed. 2004. Constitutions of the Countries of the World. Dobbs Ferry, New York: Oceana Publications.