Sidra — market town in sokólski powiat Białystok Voivodeship of Polish Republic (Second Rzeczpospolita, 1920-1939).
Information presented on the Radzima.net: 
Orthodox parish to which the market town Sidra belonged at the beginning of the 20th century;
Catholic parish to which the market town Sidra belonged at the beginning of the 20th century;
metrical books of the Catholic parish on births, marriages and deaths (with indication of years, fund, inventory and archive where parish registers kept);
Location of the market town Sidra
— geographic coordinates and depiction of the market town Sidra on early-20th-century detailed maps, modern maps, and satellite imagery (Google Maps). Administrative affiliation of the market town Sidra
— the administrative-territorial units to which the settlement belonged in different historical periods:— Russian Empire (1870-1910s), — Polish Republic (Second Rzeczpospolita, 1920-1939), Orthodox parish to which the market town Sidra belonged at the beginning of the 20th century;
Catholic parish to which the market town Sidra belonged at the beginning of the 20th century;
metrical books of the Catholic parish on births, marriages and deaths (with indication of years, fund, inventory and archive where parish registers kept);
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