Searching and synthesising ‘grey literature’ and ‘grey information’ in public health: critical reflections on three case studies

Table 1 Defining aspects and examples of ‘grey literature’, ‘grey data’, and ‘grey information’

Term	Defining aspect	Examples
Grey literature [7–9]	Not controlled by commercial publishing organisations	Internal reports, Working papers, Newsletters
Grey data [12]	User-generated, web-based	Tweets, Blogs, Facebook status updates
Grey information	Informally published or not published at all	Meeting notes, Emails, Personal memories

ISSN: 2046-4053