Exercise 1 Show that the span of the vectors 
at a
point p in `adapted coordinates' at p is a well-defined subspace of
Show that it can be identified with the null space of the
natural map 
which arises by identifying a
b-vector field as a vector field. This space is 
the b-normal
space to the smallest boundary face containing p.
Exercise 2 Show that for any interior b-map the b-differential gives
a map 
for each 
Exercise 3 Show that an interior b-map is b-normal if and only if
is surjective for each p as a map
