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LERA - Locate, Explore, Retrace and Apprehend complex text variants

LERA is an interactive, digital tool for inspecting similarities and differences between multiple versions of a text. To achieve this, LERA divides the texts into passages and displays them next to each other. Using colored highlighting, differences between versions can be located easily in a critical apparatus. LERA features a variety of tools for efficiently exploring differences between versions of texts: an interactive outline visualization (CATview), interactive word clouds and clever search functionality. This way, LERA supports the user retrace and finally apprehend the authors intentions. LERA has been developed for collating texts to provide a basis for historical critical editions. For a review from 2020, see RIDE Journal, Issue 11. Institute of Computer Science
Martin Luther University Halle-Wittenberg

News: An update on the word clouds

The November 2022 update added the latest version of stable word clouds. These keep the positions of the words spatially stable even if the data basis changes. With the help of the linked and movable selection box in the CATview overview bar, it is thus easier to trace the development of the content of a work over its length and the different text witnesses. Demo

Main features


Histoire des deux Indes

The Histoire philosophique et politique des établissements et du commerce des Européens dans les deux Indes by Abbé Raynal (1713-1796) is one of the most influential, successful and scandalous books of 18th century Europe. Its subject matter is the critical history of the european colonial expansion in ‚both’ parts of India, meaning the ‚eastern’ part of India (Asia) as well as predominantely in the ‚western’ part of India (Carribbean and Latin America). After the initial version from 1770, which was banned instantaneously in France, three more versions of the Histoire were released (1774, 1780 and posthumous 1820) containing substantial changes. Demo

Keter Shem Ṭov

The Hebrew treatise Keter Shem Ṭov (“Crown of the Good Name”) composed in the 13th century is one of the most important introductory texts into the Kabbalah, testified by about 100 differing manuscripts. The example shows an excerpt for five text witnesses. They are taken from an ongoing research project (see that prepares a scholarly edition of this work with the aid of LERA. Demo


Based on a popular fairy tale, the story of Rumpelstilzchen (engl. Rumpelstiltskin) is contained in the Kinder- und Hausmärchen by brothers Grimm (KHM 55).
This example compares the seven versions of the fairy tale published between 1812 and 1857 using a sentence-wise segmentation. Demo