Reparameterization invariants for anisotropic Bianchi I cosmology with a   massless scalar source
  Intrinsic time-dependent invariants are constructed for classical, flat, homogeneous, anisotropic cosmology with a massless scalar material source. Invariance under the time reparameterization-induced canonical symmetry group is displayed explicitly. 
D. C. Salisbury, J. Helpert, and A Schmitz