Original sentence: Modern studies of the Mongol Empire also give focus to aspects beneath the surface of events like military campaigns, conquests and imperial expansion.The death toll (by battle, massacre, flooding, and famine) of the Mongol wars of conquest is placed at about 40 million according to some sources
Edited sentence: However, modern studies of the Mongol Empire also give focus to aspects beneath the surface of events like military campaigns, conquests and imperial expansion.The death toll (by battle, massacre, flooding, and famine) of the Mongol wars of conquest is placed at about 40 million according to various sources as most of the historical writings are from the victims of Mongol conquests