  In this paper, we study the strong extension groups of Cuntz--Krieger
algebras, and present a formula to compute the groups. We also detect the
position of the Toeplitz extension of a Cuntz--Krieger algebra in the strong
extension group and in the weak extension group to see that the weak extension
group with the position of the Toeplitz extension is a complete invariant of
the isomorphism class of the Cuntz--Krieger algebra associated with its
transposed matrix.
