CaF, Rapp. Sistemi elettorali proporzionali a confronto, 2013-08-21, p. 18 ([Internet, 2017-05-18](https://www.bk.admin.ch/themen/pore/nrw/index.html?lang=it&download=NHzLpZeg7t,lnp6I0NTU042l2Z6ln1ah2oZn4Z2qZpnO2Yuq2Z6gpJCIdIF9fWym162epYbg2c_JjKbNoKSn6A--))