The goal of our study was to enhance the tools available for the study of information use and knowledge construction by developing a method for the analysis of text transformations from sources to written texts. This type of text analysis has previously been used in reading-to-write studies (see Spivey 1997; Wiley and Voss 1999) but not in information studies. We prepared our approach in a pilot study the findings of which are reported elsewhere (Sormunen and Lehtiö 2011). In this paper we introduce an extended and revised method and the findings of a larger case study where the method was applied.