sentences:  Exceptionally, in four cases in 2008, Dignitas used breathing helium gas as a suicide method instead of a pentobarbital overdose.The medical supervision was still observed, however, the prescription controlled drugs avoided, which reduced the risk of the medical board / authorities harassing the medical doctor giving a "green light" for the accompanied suicide.In two referendums on 15 May 2011, voters in the Canton of Zürich overwhelmingly rejected calls to ban assisted suicide or to outlaw the practice for non-residents.