@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}, }