@article{1978,
  author       = {Otto, Daniel and Schröder, Nadine and Diekmann, Daniel and Sander, Pia},
  issn         = {1309517X},
  journal      = {Contemporary Educational Technology},
  number       = {4},
  publisher    = {Bastas Publications},
  title        = {{Trends and Gaps in Empirical Research on Open Educational Resources (OER): A Systematic Mapping of the Literature from 2015 to 2019}},
  doi          = {10.30935/cedtech/11145},
  volume       = {13},
  year         = {2021},
}