Complex sentence: C-2 The first attempts to exploit the Green River Formation deposit was made by establishment of The Oil Shale Mining Company in 1916; however, also these attempts were unsuccessful and by 1926 the company had lost its property.
Split into simpler sentences: C-2 The first attempts to exploit the Green River Formation deposit was made by establishment of The Oil Shale Mining Company in 1916. However, also these attempts were unsuccessful and by 1926 the company had lost its property.