Heinen, R., Kerres, M., Blees, I., & Rittberger, M..  (2015).  Provisioning strong and weak OER: Requirements of open informational Ecosystems. In Open Education Global Conference 2015. Banff, Alberta, Canada . Abgerufen von https://www.researchgate.net/publication/280317907_Provisioning_strong_and_weak_OER_Requirements_of_open_informational_Ecosystems