Reference

Vojtech Mrlik, Jaroslav Hruska, Karel Poprach, Oldrich Suchy, Josef Vesely, Otokar Zavalsky (2002): Breeding distribution, population size, dynamics, ecology and protection of Montagus Harrier Circus pygargus in the Czech Republic – Ornithologischer Anzeiger – 41_2-3: 175 - 182.