Principal submatrices of normal and Hermitian matrices
Robert C. Thompson · Illinois Journal of Mathematics · 1966
values are not all distinct so let ,,, , , denote the distinct eigenvalues, where the multiplicity of is e for 1 =< i =< s; e -k -k e, n.We arrange the notation so that (x, x., ..., x) (, ..., ,, ., ..., ., ..., , -.., )