2010, A systematic review of evidence for the added benefits to health of exposure to natural environments

Diana E Bowler, Lisette M Buyung-Ali, Teri M Knight & Andrew S Pullin

BMC Public Health volume 10, Article number: 456 (2010)

https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-10-456