O'Leary, J. J., Reid, N., Hubbard, R. E., Peel, N. M. 2022. Prevalence and factors associated with advance health directives in frail older inpatients. Internal Medicine Journal. 52 (7) 1160-1166.
Hirdes, J. P., Martin, N. J. 1993. The specification of levels of active intervention in a chronic care hospital. Journal of Applied Gerontology. 12 (2) 125-138.