Gary Friend has been published by Hazardex in the UK for his paper

How to calculate an Intrinsically Safe loop approval (UK); including the impact of using Ex ic (Zone 2) and gas group on cable lengths.

https://www.hazardexonthenet.net/article/181231/How-to-calculate-an-Intrinsically-Safe-loop-approval.aspx

https://edition.pagesuite-professional.co.uk/html5/reader/production/default.aspx?pubname=&edid=5b9824ad-45a4-4386-9a82-328385e915e3&pnum=32