We denote ri x n matrices by uppercase italic letters, $$ A = \left( {\begin{array}{*{20}{c}} {{a_{11}} \ldots {a_{1n}}} \\ { \vdots \ddots \vdots } \\ {{a_{n1}} \cdots {a_{nn}}} \end{array}} \right) = ({a_{ij}}), $$ where aij E R or C. With the usual definitions of addition and scalar multiplication of matrices, $$ A + B = ({a_{ij}} + {b_{ij}}),{\text{ }}\lambda A = (\lambda {a_{ij}}), $$ the set of all n x n matrices forms a real or complex vector space. One can inter-pret this space as Rn2 (or, for complex aij, bij, A, as Cn2). Matrix multiplication is defined by $$ AB = C \Leftrightarrow {C_{ij}} = \sum\limits_{k = 1}^n {{a_{ik}}{b_{kj}}} $$