New Zealand: http://www.hpac.ca/pub/doc/NZaerotowManual.pdf
Australia: http://www.hgfa.asn.au/resources/TowManualSep05.pdf
BHPA: http://www.bhpa.co.uk/pdf/BHPA_Tech_Manual.pdf (Section 2)
Australia: http://www.hgfa.asn.au/resources/TowManualSep05.pdf
BHPA: http://www.bhpa.co.uk/pdf/BHPA_Tech_Manual.pdf (Section 2)