Update README.md with the doi of the published article

Author: JanLuca

Diff for: README.md

@@ -37,18 +37,20 @@ For detailed information how to use the package we want to point out to the [doc
 ## Citation
 
 We are happy if you want to use the framework for your research. For the citation of our work we ask to use the following references (the publication with the method description, the Zenodo reference for this Git repository and the repository itself):
-* J. Naumann, E. L. Weerda, M. Rizzi, J. Eisert, and P. Schmoll, variPEPS -- a versatile tensor network library for variational ground state simulations in two spatial dimensions (2023), [arXiv:2308.12358](https://arxiv.org/abs/2308.12358).
+* J. Naumann, E. L. Weerda, M. Rizzi, J. Eisert, and P. Schmoll, An introduction to infinite projected entangled-pair state methods for variational ground state simulations using automatic differentiation, SciPost Phys. Lect. Notes 86 (2024), doi:[10.21468/SciPostPhysLectNotes.86](https://doi.org/10.21468/SciPostPhysLectNotes.86).
 * J. Naumann, P. Schmoll, F. Wilde, and F. Krein, [variPEPS (Python version)](https://zenodo.org/doi/10.5281/zenodo.10852390), Zenodo.
 
 The BibTeX code for these references are:
 ```bibtex
-@misc{naumann23_varipeps,
-    title =         {variPEPS -- a versatile tensor network library for variational ground state simulations in two spatial dimensions},
-    author =        {Jan Naumann and Erik Lennart Weerda and Matteo Rizzi and Jens Eisert and Philipp Schmoll},
-    year =          {2023},
-    eprint =        {2308.12358},
-    archivePrefix = {arXiv},
-    primaryClass =  {cond-mat.str-el}
+@article{10.21468/SciPostPhysLectNotes.86,
+	title={{An introduction to infinite projected entangled-pair state methods for variational ground state simulations using automatic differentiation}},
+	author={Jan Naumann and Erik Lennart Weerda and Matteo Rizzi and Jens Eisert and Philipp Schmoll},
+	journal={SciPost Phys. Lect. Notes},
+	pages={86},
+	year={2024},
+	publisher={SciPost},
+	doi={10.21468/SciPostPhysLectNotes.86},
+	url={https://scipost.org/10.21468/SciPostPhysLectNotes.86},
 }
 
 @software{naumann24_varipeps_python,