Rathod S R, and Patil C Y. “Linear and Non-Linear HRV Features for the Prediction of Heart Disease Among Smokers: A Predictive Evaluation of Machine Learning Model”. International Journal of Computer Information Systems and Industrial Management Applications, vol. 12, Jan. 2020, p. 9, https://cspub-ijcisim.org/index.php/ijcisim/article/view/456.