Even in introductory textbooks on mathematical proof, intermediate proof steps are generally skipped when this seems appropriate. This gives rise to different granularities of proofs, depending on the intended audience and the context in which the proof is presented. We have developed a mechanism to classify whether proof steps of different sizes are appropriate in a tutoring context. The necessary knowledge is learnt from expert tutors via standard machine learning techniques from annotated

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... mples. We discuss the ongoing evaluation of our approach via empirical studies. * This work was supported by a grant from Studienstiftung des Deutschen Volkes e.V.