"I've searched the Internet but ..."
The PPRuNe version of Farcebooks 'You Must Share This', in that you know it's not quite right.
Slats, to save you typing the thread title into Google (other search engines are available) if you were to, you would find an amazing amount of information out there, for example
https://www.mja.com.au/journal/2005/...spective-study
Hope that helps
