Let $G$ be an amenable group and let $V$ be a finite-dimensional vector space
over an arbitrary field $\K$.
We prove that if $X \subset V^G$ is a strongly irreducible linear subshift of
finite type and
$\tau \colon X \to X$ is a linear cellular automaton, then $\tau$ is
surjective if and only if it is pre-injective. We also prove that if $G$ is
countable and $X \subset V^G$ is a strongly irreducible linear subshift, then
every injective linear cellular automaton $\tau \colon X \to X$ is surjective.
Let $G$ be a finitely generated group, $A$ a finite set of generators and $K$
a subgroup of $G$. We call the pair $(G,K)$ context-free if the set of all
words over $A$ that reduce in $G$ to an element of $K$ is a context-free
language. When $K$ is trivial, $G$ itself is called context-free; context-free
groups have been classified more than 20 years ago in celebrated work of Muller
and Schupp as the virtually free groups.