Design invariants
The author attaches, in a categorical manner, cell complexes to t-designs (which are allowed to contain repeated blocks). He then specializes to those designs with a regular group of automorphisms and shows how to take a quotient (via the group) of the cell complex to get a more easily manageable invariant. He applies the theory to help distinguish the cyclic 3-(13,4,2) designs, of which there are 33 up to isomorphism. The one invariant computed gives 25 classes 19 of which contain but one design, 2 of which have three, and the remaining 4 two.
scientific article; zbMATH DE number 3966085