Complex sentence: The Reval Governorate in the north corresponded roughly to the area of Danish Estonia and the northern portion of Riga Governorate that had a majority population of ethnic Estonians were amalgamated on April 12 (March 30 Old Style) by administrative reformes of the Russian Provisional Government.
Split into simpler sentences: The Reval Governorate in the north corresponded roughly to the area of Danish Estonia and the northern portion of Riga Governorate that had a majority of ethnic Estonians. These two areas were amalgamated on April 12 (March 30 Old Style) by administrative reformes of the Russian Provisional Government.