O’Caoimh, Rónán, et al. “Prevalence of Frailty at Population Level in European ADVANTAGE Joint Action Member States: A Systematic Review and Meta-Analysis”. Annali dell’Istituto Superiore Di Sanità, vol. 54, no. 3, Oct. 2018, pp. 226-38, https://annali.iss.it/index.php/anna/article/view/769.