diff --git a/docs/Preprocessing.md b/docs/Preprocessing.md
index b5e4b1f..f249996 100644
--- a/docs/Preprocessing.md
+++ b/docs/Preprocessing.md
@@ -14,6 +14,8 @@ OCR is based on [OCR-D](https://github.com/OCR-D)'s [ocrd_tesserocr](https://git
 
 ### Tokenization
 
+[Transformation](https://github.com/qurator-spk/neath/tree/master/tools) of [PAGE-XML](https://github.com/PRImA-Research-Lab/PAGE-XML) to [TSV](https://github.com/qurator-spk/neath/blob/master/docs/User_Guide.md#data-format).
+
 ### Named Entity Recognition
 
 For Named Entity Recognition, a [BERT-Base](https://github.com/google-research/bert) model was trained for noisy OCR texts with historical spelling variation. [sbb_ner](https://github.com/qurator-spk/sbb_ner) is using a combination of unsupervised training on a large (~2.3m pages) [corpus of German OCR](https://zenodo.org/record/3257041) in combination with supervised training on a small (47k tokens) [annotated corpus](https://github.com/EuropeanaNewspapers/ner-corpora/tree/master/enp_DE.sbb.bio). Further details are available in the [paper](https://corpora.linguistik.uni-erlangen.de/data/konvens/proceedings/papers/KONVENS2019_paper_4.pdf).