Update loo2-lfo.Rmd

[ci skip]

Author: jgabry

vignettes/loo2-lfo.Rmd

@@ -632,7 +632,7 @@ many times. For more details on approximate LFO-CV, we refer to Bürkner et al.
 
 ## References
 
-Bürkner P. C., Gabry J., & Vehtari A. (2020). Approximate leave-future-out cross-validation for Bayesian time series models. *Journal of Statistical Computation and Simulation*. [Online](https://www.tandfonline.com/doi/full/10.1080/00949655.2020.1783262). [arXiv preprint](https://arxiv.org/abs/1902.06281). 
+Bürkner P. C., Gabry J., & Vehtari A. (2020). Approximate leave-future-out cross-validation for Bayesian time series models. *Journal of Statistical Computation and Simulation*. \doi:10.1080/00949655.2020.1783262. [Online](https://www.tandfonline.com/doi/full/10.1080/00949655.2020.1783262). [arXiv preprint](https://arxiv.org/abs/1902.06281). 
 
 Vehtari A., Gelman A., & Gabry J. (2017). Practical Bayesian model evaluation using leave-one-out cross-validation and WAIC. *Statistics and Computing*, 27(5), 1413--1432. \doi:10.1007/s11222-016-9696-4. [Online](http://link.springer.com/article/10.1007/s11222-016-9696-4). [arXiv preprint arXiv:1507.04544](https://arxiv.org/abs/1507.04544).