After a referendum on 16 December 1951 it joined with WÃ 1\/4 rttemberg-Baden , which had been in the American Zone , and Baden which had also been in the French Zone , and formed the present state of Baden-W Ã 1\/4 rttemberg on 25 April 1952 A public referendum was held on 16 December 1951 . All three states were merged and the modern German state of Baden-W Ã 1\/4 rttemberg was founded on 25 April 1952 .