Yulianto, Tony, Faisol Faisol, Fatimatus Zahroh, Sri Suryanti, and Mohamad Tafrikan. 2021. “Forecasting the Recovery of COVID-19 Patients in East Java Using the Fuzzy Time Series Cheng Method”. Journal of Natural Sciences and Mathematics Research 7 (1):44-50. https://journal.walisongo.ac.id/index.php/JNSMR/article/view/11289.