update citations

doc/source/index.rst

@@ -88,4 +88,4 @@ References
 .. [1] `Foreman-Mackey et al., "Fast and Scalable Gaussian Process Modeling with Applications to Astronomical Time Series", 2017 <http://adsabs.harvard.edu/abs/2017AJ....154..220F>`_.
 .. [2] `Delisle, J.-B., Hara, N., and Ségransan, D., "Efficient modeling of correlated noise. II. A flexible noise model with fast and scalable methods", 2020 <https://ui.adsabs.harvard.edu/abs/2020A\&A...638A..95D>`_.
 .. [3] `Gordon, T. A., Agol, E., Foreman-Mackey, D., "A Fast, Two-dimensional Gaussian Process Method Based on Celerite: Applications to Transiting Exoplanet Discovery and Characterization", 2020 <https://ui.adsabs.harvard.edu/abs/2020AJ....160..240G>`_.
-.. [4] Delisle, J.-B., Unger, N., Hara, N., and Ségransan, D., "Efficient modeling of correlated noise. III. Scalable methods for jointly modeling several observables' time series with Gaussian processes", submitted to A&A.
+.. [4] `Delisle, J.-B., Unger, N., Hara, N., and Ségransan, D., "Efficient modeling of correlated noise. III. Scalable methods for jointly modeling several observables' time series with Gaussian processes", 2022 <https://ui.adsabs.harvard.edu/abs/2022A\&A...659A.182D>`_.