The specification for NTF is contained in BS 7567 - Electronic transfer
of geographic information (NTF)
ISBN 0 580 20872 9
I assume it's available from the BSI at either
BSI
2 Park Street
London
W1A 2BS
or
BSI
Linford Wood
Milton Keynes
MK14 6LE
Sorry don't know the price, as work bought it.
Steve Culshaw
NRA North West
e-mail : nra@cix.compulink.co.uk (general usage)
or sculshaw@cix.compulink.co.uk (Private - only checked at best
weekly)