-57 raised are for example: ‘Have you ever felt unsafe here? Do you feel unsafe now? In which areas have you felt unsafe? Have you ever been victimized by staff here? If yes, what did the incident(s) involve?’. The United Nations Office on Drugs and Crime (UNODC) has published simplified excerpts of the survey for prisoners used in England and Wales and encourages inspection mechanisms to develop their own questionnaires tailored to their particular national context.108 NPM Portugal – The Portuguese NPM has adapted the Measuring the Quality of Prison Life questionnaire and has been using the tool since the end of 2018 to complement its monitoring observations. It states that it has receiving very positive feedback from prisoners, who consider it a rare opportunity to express their opinion and be heard on relatively taboo topics of life in prison, like their emotions or the support received in prison. It allows comparisons of monitoring observations with survey results, points to issues to consider in future visits and allows for the analysis of long-term developments in prisons. However, it was also noted, that resources for analysing the information received through the surveys are tight.109 4.3.5. Triangulation of sources All information acquired throughout the visit (or during the preparation), for instance, survey responses, prison records and collected data as well as information collected through interviews with prison staff or managements should, if possible, be crosschecked and verified in interviews with prisoner and vice versa. This process is called triangulation.110 A final assessment should only be made at the end of the triangulation process, after enough evidence has been gathered. 108. Simplified excerpts of the survey can be seen in the UNODC, ‘Assessing Compliance with the Nelson Mandela Rules – A Checklist for Internal Inspection Mechanisms’ (2017) 75. 109. NPM Portugal, Annual Report 2018 (2019); interview with Portuguese NPM representative, 30 June 2020. 110. For more guidance on triangulation see APT, Monitoring Police Custody: A practical guide (APT 2013) 34. Monitoring Prison Violence