Fikri, M., Z. Abdul-Malek, and K. Atmadja. “Recursive Parameter Estimation and Its Convergence for Multivariate Normal Hidden Markov Model”. Thailand Statistician, vol. 23, no. 3, June 2025, pp. 657-76, https://ph02.tci-thaijo.org/index.php/thaistat/article/view/259939.