eccc.estimation(a, A, B, R, dvar, model, method="BFGS")"diagonal" for the diagonal model
and "extended" for the extended (full ARCH and GARCH parameter matrices) modeloptim.
There are three choices, namely, Nelder-Mead, BFGS (default) and CG.Nakatani, T. and T. Ter\"asvirta (2008), Appendix to Testing for Volatility Interactions in the Constant Conditional Correlation GARCH Model Department of Economic Statistics, Stockholm School of Economics, available at http://swopec.hhs.se/hastef/abs/hastef0649.htm.