Given the question: Information: - Marcin Kozubek ( born June 21 , 1978 ) is a Polish former competitive ice dancer . With Agata Baowska , he is the 1997 World Junior bronze medalist , the 1999 Polish national champion , and placed 14th at the 2000 European Championships . Kozubek started skating at the age of 8 . - Agata Baowska (; born 30 March 1978) is a Polish former competitive ice dancer. With Marcin Kozubek, she is the 1997 World Junior bronze medalist, a two-time Ondrej Nepela Memorial champion, the 1999 Winter Universiade bronze medalist, and the 1999 Polish national champion. - Marcin Kozubek (; born 21 June 1978) is a Polish former competitive ice dancer. With Agata Baowska, he is the 1997 World Junior bronze medalist, a two-time Ondrej Nepela Memorial champion, the 1999 Winter Universiade bronze medalist, and the 1999 Polish national champion. Given the paragraphs above, decide what entity has the relation 'date of birth' with '21 june 1978'.
The answer is:
marcin kozubek