  We give a simple combinatorial criterion allowing to recognize whether a
string (or, more generally, a special biserial) algebra is a laura algebra or
not. We also show that a special biserial algebra is laura if and only if it
has a finite number of isomorphism classes of indecomposable modules which have
projective dimension and injective dimension greater than or equal to two,
solving a conjecture ok Skowronski for special biserial algebras.
