@article{RichterKunterMarxetal.2021,
  author    = {Eric Richter and Mareike Kunter and Alexandra Marx and Dirk Richter},
  title     = {Who participates in content-focused teacher professional development?},
  journal   = {Frontiers in education},
  series    = {Evidence from a large scale study},
  number    = {6},
  pages     = {1 -- 10},
  doi       = {10.3389/feduc.2021.722169},
  year      = {2021},
}