Cor.5.2
Note that in case char.k = p 
then | \delta | means the smallest |d| over d \in \Z
such that d in the class \delta.
(The proof uses a bound, so it must be the smallest.)

Thm.6.3
(1) Note that | \delta | is interpreted as above.
(2) In the proof note that if r=s=2 then 
\delta_i \in \{ 0,1,-1 \} 
and if | \delta | = 1
then one of \delta_i is zero and so 
the required hom must be constructed in another way
(but this can be done - explicitly, since the rank
is low - hint: look for a 2-step rather than
1-step hom).