The paper describes the process of identifying lexical bundles, i.e. frequently recurring word sequences such as by means of and in the end of, in secondary school textbooks of history and physics. In its determination of finding genuine lexical bundles, i.e. the word boundaries between lexical bundles and surrounding arbitrary words, it proposes a new approach to come to terms with the problem of extracting overlapping bundles of different lengths. The results show that surprisingly few bundles are common to both subjects. The structural distribution across the subjects indicates that history uses more NP/PP-based and less dependent-clause-based bundles than physics. The comparative analysis manages to restrict this difference to the referential function. History almost only refers to phrases, i.e. within clauses, while physics much more tends to make references across clauses.