Report of a feasibility study to assess the availability and quality of existing data on child contact applications and domestic violence, and to identify the potential role of primary research. (gov.scot)
They used existing data from aerial surveys and distance sampling during late summer in 2006 - 2013. (sciencedaily.com)
An earlier study by the same team compared existing data from the 1990s to two million words of then newly collected data from the year 2012. (sciencedaily.com)