Please answer the following question: Information:  - Kaunas (also see other names) is the second-largest city in Lithuania and has historically been a leading centre of Lithuanian economic, academic, and cultural life. Kaunas was the biggest city and the centre of a county in Trakai Municipality of the Grand Duchy of Lithuania since 1413. In the Russian Empire it was the capital of the Kaunas Governorate from 1843 to 1915. It became the only temporary capital city in Europe during the interwar period. Now it is the capital of Kaunas County, the seat of the Kaunas city municipality and the Kaunas District Municipality. It is also the seat of the Roman Catholic Archdiocese of Kaunas. Kaunas is located at the confluence of the two largest Lithuanian rivers, the Nemunas and the Neris, and near the Kaunas Reservoir, the largest body of water entirely in Lithuania.  - Dobi - I is a plane designed by Lithuanian aviator Jurgis Dobkeviius and the first airplane of Lithuanian design . Jurgis Dobkeviius started designing and building Dobi - I in 1921 , and it was first tested by its designer in July 1922 . Soon new models Dobi - II , and Dobi - III followed . The single Dobi - I prototype was damaged in an accident beyond repair on 1 December 1925 .  - The Dobi-II is the second airplane designed by Lithuanian aviator Jurgis Dobkeviius in 1922. It was tested in October 1923. After two landing accidents plans for mass production of Dobi-II were abandoned.  - Jurgis Dobkeviius (born March 23, 1900 in Saint Petersburg, died testing his own construction airplane Dobi-III in a crash June 8, 1926 in Kaunas) was a Lithuanian aviator and aircraft designer  - Dobi-III is the third and the last aircraft designed by Lithuanian aviator Jurgis Dobkeviius. Fighter Dobi-III was designed and tested in 1924. On June 8, 1926 it crashed at Kaunas Aerodrome killing its designer.  - Saint Petersburg is Russia's second-largest city after Moscow, with five million inhabitants in 2012, and an important Russian port on the Baltic Sea. It is politically incorporated as a federal subject (a federal city). Situated on the Neva River, at the head of the Gulf of Finland on the Baltic Sea, it was founded by Tsar Peter the Great on May . In 1914, the name was changed from Saint Petersburg to Petrograd, in 1924 to Leningrad, and in 1991 back to Saint Petersburg. Between 17131728 and 17321918, Saint Petersburg was the imperial capital of Russia. In 1918, the central government bodies moved to Moscow.  - Lithuania (UK and US: ), officially the Republic of Lithuania, is a country in Northern Europe. One of the three Baltic states, it is situated along the southeastern shore of the Baltic Sea, to the east of Sweden and Denmark. It is bordered by Latvia to the north, Belarus to the east and south, Poland to the south, and Kaliningrad Oblast (a Russian exclave) to the southwest. Lithuania has an estimated population of 2.9 million people , and its capital and largest city is Vilnius. Lithuanians are a Baltic people. The official language, Lithuanian, along with Latvian, is one of only two living languages in the Baltic branch of the Indo-European language family.    Given the information, choose the subject and object entities that have the relation of 'subclass of'.
Answer:
dobi-i , aircraft