Complex sentence: Beginning with the first trips to the exclusion zone and the Oncology Center in 1987 and ending with the last trip, two months before his death, the social tragedy of society after the explosion was the basis of these studies.
Split into simpler sentences: Beginning with the first trips in 1987 to the evacuation zone and Oncology Center and ending with the last trip, two months before his death. A social tragedy of society after the explosion was the basis of these studies.