© The Author(s) (The Electronic Journal of Linear Algebra) Posted on August 13, 2014 by SCG DR Copyright Holders: © The Author(s) (The Electronic Journal of Linear Algebra) a Self-archiving policy Conditions Accepted version: √ a Published version: √ a Remarks: Authors retain the copyright of their article. Both published and accepted version is allowed to be deposited into DR-NTU. (verified by Guang Ying via email) Verification Date: 06.08.2014