The 1921 and 1930 census numbers are not accurate because 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. Warsaw, Prague, Třinec: PAI-press. OCLC177389723.
