Text this: Syntheses and crystal structures of the cerium-based coordination polymers poly[(acetic acid)bis(μ-5-carboxythiophene-2-carboxylato)bis(μ-thiophene-2,5-dicarboxylato)dicerium(III)] and poly[(μ-acetato)aqua(μ4-thiophene-2,5-dicarboxylato)cerium(III)]