New Delhi, July 27 -- There have been at least 2.7 to 3.3 million deaths due to the two waves of Covid-19 in India, estimates a study authored by Dr Prabhat Jha from Centre for Global Health Research at the University of Toronto and Dr Paul Novosad from the department of economics at Dartmouth College. India's official toll due to Covid-19 stands at just over 421,000....