de Oliveira Costa J; Bruno C; Baranwal N; Gisev N; Dobbins TA; Degenhardt L; Pearson SA, 2021, 'Variations in Long-term Opioid Therapy Definitions: A Systematic Review of Observational Studies Using Routinely Collected Data (2000-2019)', British Journal of Clinical Pharmacology, vol. 87, pp. 3706 - 3720, 10.1111/bcp.14798