Sunthornwat, R. and Sookkhee, S. 2021. Delay Time Parameter and Its Confidence Interval of Predictive Time Series of COVID-19 Outbreak Between the First and the Second Wave. Journal of Mathematical and Fundamental Sciences. 53, 2 (Oct. 2021), 306-323. DOI:https://doi.org/10.5614/j.math.fund.sci.2021.53.2.9.