@book{GrundlingLledo1999,
  author    = {Grundling, H. and Lled{\´o}, Fernando},
  title     = {Local quantum constraints},
  series = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  volume    = {402},
  journal   = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  address   = {Berlin},
  year      = {1999},
  language  = {en}
}
@article{BaumgaertelGrundling2005,
  author    = {Baumgaertel, Hellmut and Grundling, H.},
  title     = {Superselection in the presence of constraints},
  issn      = {0022-2488},
  year      = {2005},
  abstract  = {Superselection and constraints occur together in many gauge theories, and here we begin a study of such systems. Our main focus will be to analyze compatibility questions between constraining and superselection, and we will develop an example modelled on QED in which our framework is realized. We proceed from a generalization of Doplicher- Roberts superselection theory to the case of the nontrivial center, and a set of Dirac quantum constraints and find conditions under which the superselection structures will survive constraining in some form. This involves an analysis of the restriction and factorization of superselection structures. (c) 2005 American Institute of Physics},
  language  = {en}
}