Note: These are non-official reference materials by external organisations.
2016 Moja Outdoors Inc. (PDF)
David Flanagan (PDF)
British Mountaineering Council (PDF)
Hurricane Island Outward Bound School (PDF)
1995 MIT (PDF)
2008 Byron D Anderson , Physics Today (PDF)
2015 Martin Hendry, Scottish Fisheries Museum (PDF)
1993 Forbes Pettigew (PDF)
Fred Touche (PDF)
Marine Barrack, Washington DC (PDF)
2008, Alastair Buchan, Wiley Nautical (PDF)
National Environment Agency
Centre for Liveable Cities Singapore
2000, Michael Allaby, Routledge
Centre for Liveable Cities, Singapore
2019, Washington State University Extension
Sixth College UC San Diego
Bob Pikes & Christopher Buss, HRD Press
Dec 2017 singteach.nie.edu.sg (PDF)
OBI (Web Publication) [Our ED has an article in the 2019 edition off the journal pg 16-17.]
GettingSmarter.com