Clustering financial time series: New insights from an extended hidden Markov model
José Gonçalves Dias, Jeroen K. Vermunt, Sofia Ramos
European Journal of Operational Research, vol. 243, 2015, p. 852–864.

When Markets Fall Down: Are Emerging Markets All the Same?
Sofia Ramos, Jeroen K. Vermunt, José Gonçalves Dias
International Journal Of Finance And Economics, vol. 16, 2011, p. 324-338.