strategy. On 26 March 2007, after the European Union moved against the Volkswagen law, Porsche took its holding to 30.9 percent, triggering a takeover bid under German law. Porsche formally announced in a press statement that it did not intend to take over Volkswagen Group, setting its offer price at the lowest possible legal value, but intended the move to avoid a competitor taking a large stake, or to stop hedge funds dismantling Volkswagen Group, which is Porsche's most important partner. On 16 September 2008, Porsche announced that the company had increased its stake in Volkswagen AG to 35 percent. By October 2008, Porsche held 42.6 percent of Volkswagen AG's ordinary shares, and held stock options on another 31.5 percent. thus, effectively holding over 74 percent; 42.6 percent actual shares, and the rest as convertible options. Volkswagen AG briefly became the world's most valuable company, as the stock price rose to over €1,000 per share as short sellers tried to cover their positions. The substantial investment in Volkswagen left Porsche with huge financial burden with its debts accumulating up to 13 billion euros by 2009. Porsche would get emergency infusion of about a billion dollars from Volkswagen. In July 2012, Volkswagen completed takeover of Porsche ending the 4 year saga and formed an integrated automotive group with Porsche. Porsche AG would become the 10th brand of Volkswagen. The holding company Porsche SE was left with 31 percent of the subscribed capital of Volkswagen AG, and 50.7 percent of the voting rights in the company. , share ownership of Volkswagen AG is distributed as follows: Stock market listings Volkswagen AG shares are primarily traded on the Frankfurt Stock Exchange, and are listed under the 'VOW' and 'VOW3' stock ticker symbols. First listed in August 1961, the shares were issued at a price of DM 350 per DM 100 share, Volkswagen AG shares are now separated into two different types or classes: 'ordinary shares' and 'preference shares'. The ordinary shares are now traded under the WKN 766400 and ISIN DE0007664005 listings, and the preference shares under the WKN 766403 and ISIN DE0007664039 listings. Volkswagen AG shares are also listed and traded on other major domestic and worldwide stock exchanges. In Germany's domestic exchanges, since 1961 these include those in Berlin, Düsseldorf, Hamburg, Hanover, Munich and Stuttgart. International exchanges include those in Basel (listed in 1967), Geneva (1967), Zürich (1967), Luxembourg (1979), London