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.