APA

Prosnak J., . (1970). The Frédéric Chopin international piano competitons, Warsaw 1927-1970. Warsaw: .

Chicago

Prosnak Jan, . 1970. The Frédéric Chopin international piano competitons, Warsaw 1927-1970. Warsaw: .

Harvard

Prosnak J., . (1970). The Frédéric Chopin international piano competitons, Warsaw 1927-1970. Warsaw: .

MLA

Prosnak Jan, . The Frédéric Chopin international piano competitons, Warsaw 1927-1970. Warsaw: . 1970.