Complex sentence: The first three locomotives were delivered in 1931, numbered in the range from NG17 to NG19, followed by three more in 1939, numbered in the range from NG117 to NG119.
Split into simpler sentences: The first three locomotives were delivered in 1931, numbered in the range from NG17 to NG19. They were followed by three more in 1939, numbered in the range from NG117 to NG119.