of the world's two superpowers for four decades after World War II through its hegemony in Eastern Europe, military strength, economic strength and scientific research, especially in space technology and weaponry. Post-Soviet states The analysis of the succession of states for the 15 post-Soviet states is complex. The Russian Federation is seen as the legal continuator state and is for most purposes the heir to the Soviet Union. It retained ownership of all former Soviet embassy properties, and also inherited the Soviet Union's UN membership, with its permanent seat on the Security Council. Of the two other co-founding states of the USSR at the time of the dissolution, Ukraine was the only one that had passed laws, similar to Russia, that it is a state-successor of both the Ukrainian SSR and the USSR. Soviet treaties laid groundwork for Ukraine's future foreign agreements as well as leading to the country agreeing to undertake 16.37% of debts of the Soviet Union for which it was going to receive its share of the USSR's foreign property. Russia's position as the 'only continuation of the USSR' that became widely accepted in the West, as well as constant pressure from the Western countries, allowed Russia to dispose state property of USSR abroad and conceal information about it. Due to that Ukraine never ratified 'zero option' agreement that Russian Federation had signed with other former Soviet republics, as it denied disclosing of information about Soviet Gold Reserves and its Diamond Fund. The dispute over former Soviet property and assets between the two former republics is still ongoing: Similar situation occurred with restitution of cultural property. Although on 14 February 1992 Russia and other former Soviet republics signed agreement 'On the return of cultural and historic property to the origin states' in Minsk, it was halted by the Russian State Duma that eventually passed 'Federal Law on Cultural Valuables Displaced to the USSR as a Result of the Second World War and Located on the Territory of the Russian Federation' which made restitution currently impossible. Estonia, Latvia, and Lithuania consider themselves as revivals of the three independent countries that existed prior to their occupation and annexation by the Soviet Union in 1940. They maintain that the process by which they were incorporated into the Soviet Union violated both international law and their own law, and that in 1990–1991 they were reasserting an independence that still legally existed.