The 1921 and 1930 census numbers are not accurate since nationality depended on self-declaration and many Poles declared Czech nationality mainly as a result of fear of the new authorities and as compensation for some benefits. Cf. Zahradnik, Stanisław· Marek Ryczkowski (1992). Korzenie Zaolzia. Warszawa - Praga - Trzyniec: PAI-press. OCLC177389723.
