Problems of International Astronomy Olympiad (2011)

Problems: http://www.issp.ac.ru/iao/

Problems of International Astronomy Olympiad (2015)

Main webpage: http://www.issp.ac.ru/iao/2015/iao15_e.html

Problems link: http://www.issp.ac.ru/iao/2015/booklet/index_e.html