The results of a survey of Finnish windmills have been made available online.
You can view the survey here: http://www.sustainableheritage.eu/windmills-in-finland/. It covers 383 post mills, 53 hollow post mills and 51 smock mills – the three main types of windmill found in Finland. A glossary of Finnish mill terms is also available.
Earlier studies of Finnish windmills were carried out in the 1960s and 1970s by Rex Wailes and Auvo Hirsjärvi. The Mills Archive holds the Rex Wailes collection of FInnish material, which was catalogued as part of a summer internship project last year. You can view the collection here: http://catalogue.millsarchive.org/finnish-mills-material and read about it here: https://new.millsarchive.org/2015/07/07/mills-of-finland/.