@misc{indiciae40e3ec9c66cf,
  title = {Symmetry superposition studied by surface second-harmonic generation.},
  author = {G Lüpke and G Marowsky and R Steinhoff and A Friedrich and B Pettinger and DM Kolb},
  year = {1990},
  doi = {10.1103/physrevb.41.6913},
  url = {https://pubmed.ncbi.nlm.nih.gov/9992947/},
  note = {Source identifier: 9992947}
}