This section presents models of the volatility in rubber spot and futures prices returns,
namely the CCC model [2], VARMA-GARCH model [7], VARMA-AGARCH model [9],
and DCC model [4] (see [8] for a comprehensive discussion and comparison of these
models in terms of their mathematical and statistical properties). The typical specifications
underlying the multivariate conditional mean and conditional variance in returns are given
as follows: