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

Abstract in brief

• This text discusses the challenges and methods involved in locating and synthesizing grey literature and grey information—types of data not controlled by traditional publishers and often hard to find—in public health research.
• It reflects on three case studies where the authors tried to systematically search and analyze grey literature, highlighting issues like search efficiency, data management, and the importance of including grey sources to understand public health interventions.
• The authors emphasize that adapting standard systematic review methods to grey literature is essential because much of the practical knowledge and evaluation data in public health exists outside formal publications, making these sources critical for comprehensive evidence synthesis.