Discrete Mathematics
Equipartitions of graphs.
D. Eppstein, J. Feigenbaum, and C.L. Li.
Discrete Mathematics 91 (3): 239–248, 1991.Considers partitions of the vertices of a graph into equal subsets, with few pairs of subsets connected by edges. (Equivalently we view the graph as a subgraph of a product in which one factor is sparse.) A random graph construction shows that such a factorization does not always exist.