Key references: Patient-reported pain severity

Cleeland C, Pain Research Group of the WHO Collaborating Centre for Symptom Evaluation in Cancer Care. The Brief Pain Inventory (short form). Houston, TX: The University of Texas MD Anderson Cancer Center; 1991. https://www.mdanderson.org/research/departments-labs-institutes/departments-divisions/symptom-research/symptom-assessment-tools/brief-pain-inventory.html
Hicks CL, von Baeyer CL, Spafford PA, van Korlaar I, Goodenough B. The Faces Pain Scale-Revised: toward a common metric in pediatric pain measurement. Pain 2001;93(2):173–83. https://www.ncbi.nlm.nih.gov/pubmed/11427329
Krebs EE, Lorenz KA, Bair MJ, Damush TM, Wu J, Sutherland JM, et al. Development and initial validation of the PEG, a three-item scale assessing pain intensity and interference. J Gen Intern Med 2009;24(6):733–8. https://www.ncbi.nlm.nih.gov/pubmed/19418100
Malviya S, Voepel-Lewis T, Burke C, Merkel S, Tait AR. The revised FLACC observational pain tool: improved reliability and validity for pain assessment in children with cognitive impairment. Paediatr Anaesth 2006;16(3):258–65. https://www.ncbi.nlm.nih.gov/pubmed/16490089
Schug S, Palmer GM, Scott DA, Halliwell R, Trinca J, APM:SE Working Group of the Australian and New Zelanand College of Anaesthetists and Faculty of Pain Medicine, editors . Acute pain management: scientific evidence. 4th ed. Melbourne: Australian and New Zealand College of Anaesthetists and Faculty of Pain Medicine; 2015. https://www.anzca.edu.au/safety-advocacy/advocacy/college-publications