 The ballads are cross referenced to the corresponding TSB number ("The Types of the Scandinavian Medieval Ballad").Not only that, the "SMB" numbers were assigned in the order of ascending TSB type numbers, i.e., SMB 1 was assigned to TSB A 4, ending with SMB 260 assigned to F 75, at the point in time when 260 ballad types were recognized in the collection.But 263 types were given in the final count when the 5th volume was published 2001.