Complex sentence: New studies were initiated in the early 1970s based on factual information, however under the influence of the Soviet historiography, Polish historians continued to expound the mistaken Soviet concept of Ukrainian bourgeoise nationalists, although viewed in their own specific manner.
Split into simpler sentences: New studies were initiated in the early 1970s based on factual information. Under the influence of the Soviet historiography, Polish historians continued to expound the mistaken Soviet concept of Ukrainian bourgeoise nationalists, viewed in their own specific manner.