For data extraction and validation, the research team was divided into four pairs, ensuring that each article was assessed separately by at least two research team members. The pairs received batches of 20 articles at a time. Variations in the assessments were discussed until consensus was reached within the pair(s). Further, queries detected within the pairs were raised and discussed with the whole research team, until consensus was achieved. Regular whole-team online meetings were held to consolidate findings between every new batch of articles and throughout the development and analysis process. In total, the group had > 20 online meetings and four face-to-face meetings from the initial establishment of the group in January 2015.