A: This is not always a given. So far there is no quality seal for OER materials. Open user comments, peer review, and the publication of materials on platforms of established institutions like e.g. universities can provide a first indication of quality. Just as with printed text materials, quality can though not be guaranteed. This unsettles many users. The actuality and adaptability of the materials nevertheless speaks for the use of OER. At the end of the day, you only know yourself whether the selected material is suitable for the intended purpose and whether its content is correct.