2Halim Ozdemir,Ahmet Angar Ozban. On idempoteney of linear combinations of idempotent matrices [J]. Applied Mathematics and Computation, 2004,159(2) : 439-- 448.
3Oskar Maria Baksatary. Idempotency of linear combinations of three idempotent matrices,two of which are disjoint[J]. Linear Algebra and Its Applications, 2004,388: 67--78.
4Oskar Maria Baksalary,j ulio Benitez. Idempotency of linear combinations of three idempotent, two of which are commuting [J ]. Linear Algebra and Its Applications, 2007,424:320--337.
5Bart H,Ehrhardt T,Silbermann B. Zero sums of idempotents in Banach algebras[J]. Linear and Multilinear Algebra,1994,19(2) :125--134.
6Gross J,Trenkler G. Nonsingularity of defference of two oblique projectors[J]. SIAM J Matrix Anal Appl, 1999, 213(2): 390-395.
7Koliha J J, Rakocevic V, Straskraba I. The difference and sum of proiectors [J ]. Linear Algebra and Its Applications, 2004,388 : 279--288.
8Jeriy K Baoksalary,Oskar Maria Baksalary. Nonsingularity of linear combinations of idempotent matrices[J]. Linear Algebra and its Applications,2004,388:25-29.
9Du Hongke, Yao Xiycun, Keng Chunyuan. Invertiblity of linear combinations of two idempotents[J]. Proceedings of the American Mathematical Society, 2005,34 (5) : 1451 --1457.
10Zhang Fuzhen. Matrix theory: basic results and techniques [ M]. New York .. Springer, 1999.