@article{FresardHackenbergerKopp2018,
  author    = {Raymond Fr{\´e}sard and Christian Hackenberger and Thilo Kopp},
  title     = {Magnetic transitions in strong coupling expansions for nearly degenerate states},
  journal   = {Annalen der Physik},
  volume    = {524},
  number    = {8},
  pages     = {411 -- 420},
  doi       = {10.1002/andp.201200031},
  year      = {2018},
}