  Frequentely it happens that isogenous (in the sense of Mukai) K3 surfaces are
partners of each other and sometimes they are even isomorphic. This is due, in
some cases, to the (too high, e.g. bigger then or equal to 12) rank of the
Picard lattice as showed by Mukai in [Muk3]. In other cases this is due to the
structure of the Picard lattice and not only on its rank. This is the case, for
example, of K3s with Picard lattice containing a latice of Todorov type (0,9)
or (0,10)
