[Rules] Advanced Armor Operations

[Geoff Curran]

Hi.   I hope this is the right place to ask......

5.3 says that a unit cannot enter a hex with an enemy unit unless in an assault or 'Advanced Armour Operations (Optional rule).  But I cannot find Advanced Armour Operations in the optional rules (Fourth Edition from Crete).   Could someone direct me to where this is ?   Much appreciated.