Before revision:  We prove that the condition number of NOSAS methods do not depend on the coefficients , and with a specific choice of the threshold of the eigenvalues, we can obtain condition numbers for the preconditioned system similar to the AAS method with constant coefficients .
After revision:  To achieve the low-rank, we solve a generalized eigenvalue problem in each subdomain. NOSAS have the minimum energy for a given rank of the coarse space. The condition number of NOSAS methods do not depend on the coefficients , and with a specific choice of the threshold of the eigenvalues, we can obtain condition numbers for the preconditioned system similar to the AAS method with constant coefficients .