Complex sentence: After 20 years study, in 1687 Witsen published the first map of Siberia, and in 1692 a treatise titled "Noord en Oost Tartaryen", describing Siberia and the surrounding areas, though without literary references.
Split into simpler sentences: After 20 years study, in 1687 Witsen published the first map of Siberia. In 1692 he published a treatise titled "Noord en Oost Tartaryen", describing Siberia and the surrounding areas, though without literary references.