In this task, you're given a statement, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.

Context: United States Air Force F-15s and F-16s flying mainly from Italian air force bases attacked the defending Yugoslav fightersusually MiG-29s, which were in bad shape, due to lack of spare parts and maintenance. Link Information: The Mikoyan MiG-29 (; NATO reporting name: Fulcrum) is a twin-engine jet fighter aircraft designed in the Soviet Union. Question: Which country designed the fighter planes that the Yugoslav Air Force used but were badly maintained?
Answer: Soviet Union