Complex sentence: The coming of World War I, coupled with a serious fuel crisis, accelerated these studies and in 1916, a group of geologists led by Nikolay Pogrebov were sent to Estonia to organize the mining of oil shale and its transportation to St. Petersburg.
Split into simpler sentences: The coming of World War I, coupled with a serious fuel crisis, accelerated these studies. In 1916, a group of geologists led by Nikolay Pogrebov were sent to Estonia to organize the mining of oil shale and its transportation to St. Petersburg.