Merge pull request #111 from DoubleML/m-fix-urls-in-vignette

links / urls did not pass checks on CRAN

Author: MalteKurz

vignettes/Introduction_to_DoubleML.Rmd

@@ -28,7 +28,7 @@ Estimation of nuisance components can be performed by various state-of-the-art m
 
 Bach, P., Chernozhukov, V., Kurz, M. S., and Spindler, M. (2021), DoubleML - An Object-Oriented Implementation of Double Machine Learning in R, arXiv:[2103.09603](https://arxiv.org/abs/2103.09603).
 
-Chernozhukov, V., Chetverikov, D., Demirer, M., Duflo, E., Hansen, C., Newey, W. and Robins, J. (2018), Double/debiased machine learning for treatment and structural parameters. The Econometrics Journal, 21: C1-C68, URL: https://academic.oup.com/ectj/article/21/1/C1/5056401.
+Chernozhukov, V., Chetverikov, D., Demirer, M., Duflo, E., Hansen, C., Newey, W. and Robins, J. (2018), Double/debiased machine learning for treatment and structural parameters. The Econometrics Journal, 21: C1-C68, URL: <https://doi.org/10.1111/ectj.12097>.
 
-Lang, M., Binder, M., Richter, J., Schratz, P., Pfisterer, F., Coors, S., Au, Q., Casalicchio, G., Kotthoff, L. and Bischl, B. (2019), mlr3: A modern object-oriented machine learing framework in R. Journal of Open Source Software, doi:10.21105/joss.01903, URL:  https://mlr3.mlr-org.com/.
+Lang, M., Binder, M., Richter, J., Schratz, P., Pfisterer, F., Coors, S., Au, Q., Casalicchio, G., Kotthoff, L. and Bischl, B. (2019), mlr3: A modern object-oriented machine learing framework in R. Journal of Open Source Software, <https://doi.org/10.21105/joss.01903>, URL:  https://mlr3.mlr-org.com/.