Verma, V., Uraiya, D., Kumar, A., Tripathi, N. and Dhoan, P. (2017) “A study of the correlation of non-motor symptoms of Parkinson’s disease and Parkinson plus syndrome with duration of the disease”, International Journal of Medical Research and Review, 5(8), pp. 814-819. doi: 10.17511/ijmrr.2017.i08.07.