In Power system islanding Dimension reduction is obtained for the Lyapunov Matrix via link and do not link on generator nodes . It would be helpful if a numerical example giving a clear picture of this construction is available . Most references state pairwise constraints to be ordered as two columns, but there seem to be many possible solutions. It is hoped ,that insight from answers, would help in understanding what is the best solution and what exactly is the role of SVD on the Lyapunov matrix in terms of output graph of reduced dimension.