  Let A be the mod 2 Steenrod algebra, and let Q denote the category of
exterior sub-Hopf algebras of A, where the morphisms are given by inclusions.
The restriction maps Ext_A (Z/2,Z/2) --> Ext_E (Z/2,Z/2), for E in Q, can be
assembled into a map
  i:Ext_A (Z/2, Z/2) --> lim_Q Ext_E (Z/2,Z/2).
  There is an action of A on this inverse limit, and i factors through the
invariants under this action, giving a map
  g:Ext_A (Z/2, Z/2) --> ( lim_Q Ext_E (Z/2,Z/2) )^A.
  We show that g is an F-isomorphism.
