UpperNu() and LowerNu() print the numerical upper and lower bounds for the degree
of freedom parameter of the Student--t distribution, std. (including also sstd and mvt). UpperA() and LowerA() print the numerical upper and lower bounds for the score parameter
in the GAS recursion. These bounds are applied to each diagonal element of the matrix A that premultiplies the scaled score. UpperB() and LowerB() print the numerical upper and lower bounds for the autoregressive
parameter in the GAS recursion. These bounds are applied to each diagonal element
of the matrix B that premultiplies the past value of the parameters.