Note on aligned Petrov type D purely magnetic perfect fluids
  We recently showed (Class. Quantum Grav.\ 23, 3353; gr-qc/0602091) that aligned Petrov type D purely magnetic perfect fluids are necessarily locally rotationally symmetric (LRS) and hence are all explicitly known. We provide here a more transparent proof. 
Lode Wylleman and Norbert Van den Bergh