which maps every matrix in the representation into the same pattern upper triangular blocks. Every ordered sequence minor block is a group subrepresentation. That is to say, if the representation is, for example, of dimension 2, then we have: D ′ ( a ) = P − − 1 D ( a ) P = ( D ( 11 ) ( a ) D ( 12 ) ( a ) 0 D ( 22 ) ( a ) ) ,