@misc{gfp_map_sl_2_r_to_psl_2_r,
  author = {{Groups for Physics}},
  title = {SL(2, R) → PSL(2, R)},
  howpublished = {Groups for Physics reference},
  url = {https://groups.qft.org/atlas/maps/sl-2-r-to-psl-2-r/},
  version = {2026.11-workbench.4},
  note = {Research workbench IV; review status recorded on canonical page}
}