Publications

1. K. Ziętak, On the optimum rational function connected with the ADI-method, Applicationes Mathematicae 11 (1970), 337-352.
2. G. Kozłowski, W.J. Ziętek, K. Ziętak, Theory of the thickness- dependence of the domain width in regular layer-like domain structures of uniaxial ferromagnets, Acta Physica Polonica A 42 (1972), 87-106.
3. K. Ziętak, Construction and features of the optimum rational function used in ADI-method, Applicationes Mathematicae 14 (1974), 277-311.
4. K. Ziętak, Investigations of the algorithms determining the optimum rational function of the ADI - method, Applicationes Mathematicae 14 (1974), 419-439.
5. K. Ziętak, Double Chebyshev series for hypergeometric functions of two variables, Bulletin de L'Academie Polonaise des Sciences, Serie des sciences math., astr. et phys. 233 (1975), 1107-1111.
6. K. Ziętak, The properties of the minimax solution of a non-linear matrix equation XY=A, IMA Journal of Numerical Analysis 3 (1983), 229-244.
7. K. Ziętak, The lp-solution of the nonlinear matrix eqution XY=A, BIT 23 (1983), 248-257.
8. K. Ziętak, The Chebyshev approximation of a rectangular matrix by matrices of smaller rank as the limit of lp-approximation, Journal of Computational Applied Mathematics 11 (1984), 297-305.
9. K. Ziętak, The lp-solution of the linear matrix equation AX+YB = C, Computing 32 (1984), 153-162.
10. K. Ziętak, On a particular case of the inconsistent linear matrix equation AX+YB = C, Linear Algebra and Its Applications 66 (1985), 249-258.
11. K. Ziętak, The Chebyshev solution of the linear matrix equation AX+YB=C, Numerische Mathematik 46 (1985), 455-478.
12. K. Ziętak, Properties of the approximate generalized inverses of a class of matrices, Linear Algebra and Its Applications 92 (1987), 259-272.
13. K. Ziętak , Properties of the l1-solution of the linear matrix equation AX+YB=C, IMA Journal of Numerical Analysis 7 (1987), 223-233.
14. K. Ziętak, On the characterization of the extremal points of the unit sphere of matrices, Linear Algebra and Its Applications 106 (1988), 57-75.
15. K. Ziętak, Properties of the approximations of a matrix which lower its rank, IMA Journal of Numerical Analysis 9 (1988), 545-554.
16. K. Ziętak, Evaluation of coefficients of a double Chebyshev series of the function g(p(x+y)), Applicationes Mathematicae 20 (1988), 137-140.
17. K.K. Lau, K. Ziętak, A note on linear approximation of matrices, Applicationes Mathematicae 21 (1991), 257-263.
18. K. Ziętak, Properties of linear approximations of matrices in the spectral norm, Linear Algebra and Its Applications 183 (1993), 41-60.
19. K. Ziętak, Subdifferentials, faces and dual matrices, Linear Algebra and Its Applications 185 (1993), 125-141.
20. K. Ziętak, Strict approximation of matrices, SIAM J. Matrix Anal. Appl. 16 (1995), 232-234. Abstract
21. P. Zieliński, K. Ziętak, Polar decomposition - properties, applications and algorithms, Applied Mathematics, Annals of the Polish Mathematical Society 38 (1995), 24-49. Abstract
22. K. Ziętak, On approximation problems with zero-trace matrices, Linear Algebra and Its Applications 247 (1996), 169-184. Abstract
23. K. Ziętak, Strict spectral approximation of a matrix and some related problems, Applicationes Mathematicae 24 (1997), 267-280. Abstract
24. K. Ziętak, Orthant - monotonic norms and overdetermined linear systems, J. Approx. Theory 88 (1997), 209-227. Abstract
25. A. Bartkowiak, K. Ziętak, Correcting possible non-positivness of a covariance matrix estimated element wise in a robust way, in Proc. of Advanced Computer Systems, Szczecin 2000, 91-96. Abstract
26. A. Bartkowiak, K. Ziętak, Backprojection of data vector using a given covariance matrix, in Proc. of Advanced Computer Systems, Mielno 2001 (eds H.J. Soldek, J. Pejas), Kluwer 2002, 27-38. Abstract
27. K. Ziętak, Properties of the strict spectral approximation of a complex matrix, Opuscula Mathematica 22 (2002), 41-46. Abstract
28. A. Kiełbasinski, K. Ziętak, Numerical behaviour of Higham's scaled method for polar decomposition, Numerical Algorithms 32 (2003), 105-140. Abstract
29. B. Laszkiewicz, K. Ziętak, Approximation of matrices and family of Gander methods for polar decomposition, BIT Numer. Math. 46 (2006), 345-366. Abstract
    online 3 May 2006: DOI:10.1007/s10543-005-0053-4
30. B. Laszkiewicz, K. Ziętak, Approximation by matrices with restricted spectra, Linear Algebra nad Its Applications 428 (2008), 1031-1040. Abstract
    online 30 October 2007: DOI:10.1016/j.laa.2007.09.009
31. B. Laszkiewicz, K. Ziętak, Numerical experiments with algorithms for the ADI and Zolotarev coefficients, Applied Mathematics and Computation 206 (2008), 298-312, Abstract
    online 13 September 2008: DOI:10.1016/j.amc.2008.08.055
32. B. Laszkiewicz, K. Ziętak, Algorithms for the matrix sector function, Electronic Transactions on Numerical Analysis 31 (2008), 358-383. Abstract
33. 33. B. Laszkiewicz, K. Ziętak, A Pade family of iterations for the matrix sector function and the matrix pth root, Numerical Linear Algebra with Applications 16 (2009), 951-970, Abstract
    online 2 July 2009: DOI: 10.1002/nla.656,
34. 34. A. Kiełbasiński, K. Ziętak, Note on ``A new scaling for Newton's iteration for the polar decomposition and its backward stability" by R. Byers and H. Xu, SIAM J. Matrix Anal. Appl., 31 (2010), 1538-1539. Abstract
    online 8 January 2010: simax/31-3/74012.html
35. I. Wróbel, K. Ziętak, On the Legendre-based filters of Persson and Strang, Applied Mathematics and Computation 218 (2011), 4216-4233. Abstract
    online 9 November 2011: DOI: dx.doi.org/10.1016/j.amc.2011.09.053
36. O. Gomilko, F. Greco, K. Ziętak, A Pade family of iterations for the matrix sign function and related problems, Numerical Linear Algebra with Applications 19 (2012), 585-605. Abstract
    online 24 April 2011: DOI: onlinelibrary.wiley.com/doi/10.1002/nla.786
37. O. Gomilko, D.B. Karp, M. Lin, K. Ziętak, Regions of convergence of a Pade family of iterations for the matrix sector function and the matrix pth root, Journal of Computational and Applied Mathematics 236 (2012), 4410-4420. Abstract
    online 19 April 2012: DOI: dx.doi.org/10.1016/j.cam.2012.04.007
38. K. Ziętak, The dual Pade families of iterations for the matrix pth root and the matrix p-sector function, Journal of Computational and Applied Mathematics 272 (2014), 468-486. Abstract
    online 6 August 2013: DOI: dx.doi.org/10.1016/j.cam.2013.07.021
39. J.R. Cardoso, K. Ziętak, On a sub-Stiefel Procrustes problem arising in computer vision, Numerical Linear Algebra with Applications 22 (2015), 523-547, Abstract
    Early View 26 Feb. 2015, DOI:onlinelibrary.wiley.com/doi/10.1002/nla.1969
40. A. Kiełbasiński, P. Zieliński, K. Ziętak, On iterative algorithms for the polar decomposition of a matrix and the matrix sign function, Applied Mathematics and Computation 270 (2015), 483--495.
    Early View, 31 August 2015
    online: DOI: dx.doi.org/10.1016/j.amc.2015.08.004
41. K. Ziętak, From the strict Chebyshev approximant of a vector to the strict spectral approximant of a matrix, Banach Center Publications vol. 112 (2017), 307-346. Abstract
    DOI: dx.doi.org/10.4064/bc112-0-16