9.G
Nightrider seems to have got it correct, the reference is in Eu ops subpart Q - I'm afraid I'm not clever enough to put a link in, but if you google it you will find Eu ops in its entirety as a downloadable pdf. The 13 hours may be extended up to 14 hours twice in seven days as a planned rostered duty. As you are allowed 2 hours discretion on a 13 hour day you are allowed 1 hour on top of a 14 hour day ie up to 15 hours maximum - that would then be reduced for extra sectors, time in the WOCL etc. Certainly whre I work this is the way that the rules are implemented and is as published in the ops manual.
BOAC
The 13 hours is the max duty for a two sector day under Eu ops subpart Q FTLs. It is shortened for multiple sectors and flights at stupid oclock (Window of circadian low or WOCL) in a similar manner to the way that FDPs are adjusted in cap 371 for late finishes and early starts.
Hope that helps. Personally I find cap371 to be far more user friendly, but maybe that's just because I've used it for so long.