Complex sentence: The publication in 1835 of the Finnish national epic, "Kalevala", was a founding stone of Finnish nationalism and ethnogenesis, while Finnish became the official language of Finland only in 1892.
Split into simpler sentences: The publication in 1835 of the Finnish national epic, "Kalevala", was a founding stone of Finnish nationalism and ethnogenesis. Finnish was recognized as the official language of Finland only in 1892.