Morris, TP;    van Smeden, M;      (2022)    Causal analyses of existing databases: The importance of understanding what can be achieved with your data before analysis (commentary on HernĂ¡n).                   Journal of Clinical Epidemiology , 142    pp. 261-283.    10.1016/j.jclinepi.2021.09.026 <https://doi.org/10.1016/j.jclinepi.2021.09.026>.       Green open access