add preprint link documentation

docs/source/index.rst

@@ -39,17 +39,21 @@ The following features are currently included:
 * line length 
 * and more...
 
+Find here the preprint of **py_neuromodulation** called *"Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants"* [1]_.
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 How can those features be used?
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-The original intention for writing this toolbox was movement decoding from invasive brain signals [1]_.
+The original intention for writing this toolbox was movement decoding from invasive brain signals [2]_.
 The application however could be any neural decoding and analysis problem.
 *py_neuromodulation* offers wrappers around common practice machine learning methods for efficient analysis.
 
 References
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-.. [1] Merk, T. et al. *Electrocorticography is superior to subthalamic local field potentials for movement decoding in Parkinson’s disease*. Elife 11, e75126, `https://doi.org/10.7554/eLife.75126` (2022).
+.. [1] Merk, T. et al. *Invasive neurophysiology and whole brain connectomics for neural decoding in patients with brain implants*, `https://doi.org/10.21203/rs.3.rs-3212709/v1` (2023).
+.. [2] Merk, T. et al. *Electrocorticography is superior to subthalamic local field potentials for movement decoding in Parkinson’s disease*. Elife 11, e75126, `https://doi.org/10.7554/eLife.75126` (2022).