Update README.md

Author: mstorath

README.md

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 This is a reference implementation in Matlab for the algorithms described in the paper
 
-**[M. Storath, A. Weinmann, "Smoothing splines for discontinuous signals", 2022](
-https://doi.org/10.48550/arXiv.2211.12785)**
+**M. Storath, A. Weinmann, "Smoothing splines for discontinuous signals", to appear in Journal of Computational and Graphical Statistics, 2023, [[Preprint](
+https://doi.org/10.48550/arXiv.2211.12785)]**
 
 ## Overview of main functionalities
 1. **cssd.m** computes a cubic smoothing spline with discontinuities (CSSD) for data (x,y). It is a solution of the following model of a smoothing spline $f$ with a-priori unknown discontinuities $J$