Complex sentence: The several District Gazetteers published by the Government (1880,1908,1995) were reliable reports on the Nilgiris, its economy, demography and culture, but have to some extent been superseded by the "Encyclopaedia of the Nilgiri Hills" (2012).
Split into simpler sentences: The several District Gazetteers published by the Government (1880,1908,1995) were reliable reports on the Nilgiris District, its economy, demography and culture. They have been superseded by the "Encyclopaedia of the Nilgiri Hills" (2012).