Decoding Mod Index

[Tony Renshaw <renshaw@ozemail.com.au>]

Gidday, 
Just a quick question for those more intelligent than me. What does A/R in
the applicability column mean for optional mods? Mod No. 18 (Pitot
Positioning)  mentions Page 7-10 & ff Issue 3.What is ff,and where are the
pages applicable, or have they been removed in my manual and replaced with
the mod summary in the front? I drastically miss an index. Anybody else feel
the same
 Any tips would help!
Regards 
Tony Renshaw