Complex sentence: After that, over 70 books of poems and stories where published from him, possibly the most famous of these are the two Helkavirsiä-collections (1903 and 1916), in which he extensively uses Finnish mythology and folklore.
Split into simpler sentences: After that, over 70 books of poems and stories were published by him. Possibly the most famous of these are the two Helkavirsiä-collections (1903 and 1916), in which he extensively uses Finnish mythology and folklore.