Educational quizzes are useful not only to evaluate or test the knowledge acquired by a learner, but also to help her/him to deepen knowledge about a specific domain or topic in an informal and entertaining way. The production of quizzes is a time-consuming task that can be automated by taking advantage of existing knowledge bases available on the Web of Linked Open Data (LOD). However, automatically extracting from the LOD a knowledge graph composed by the information of a set of resources which are relevant to a given specific domain or topic, is a crucial phase for the automatic generation of quizzes. To address this issue, we propose a heuristic that extracts from DBpedia a set of resources related to a given specific domain. Such heuristic has been implemented and used for the automatic generation of quizzes in the geography and privacy domains. We report a comparative user evaluation of it.