Siljan Ring proved inconclusive. Drilling for natural gas was resumed in the late 2000s and continues as of mid-2012. The scientific premise for prospecting of this sort is based on the work of physicist Vladimir Kutcherov, who is cooperating with Igrene, the company financing the drilling operations. Siljan Ring The Siljan Ring () is a prehistoric impact crater in Dalarna, central Sweden. It is one of the 15 largest known impact craters on Earth and the largest in Europe, with a diameter of about . The impact that created the Siljan Ring occurred when a meteorite collided with the Earth's surface during
Trans-European Airport network Trans-European Airport network The Trans-European Airport network is one of a number of the Trans-European Transport Networks (TEN-T) of the European Union. According to Article 13 of the Decision No 1692/96/EC of the European Parliament and of the Council of 23 July 1996 on Community guidelines for the development of the trans-European transport network, the Trans-European Airport network comprises airports situated within the territory of the Community which are open to commercial air traffic. Similarly to the seaports included in the Trans-European Transport network, the airports must correspond to one of the following three categories of connecting points: A. International