Add BLAKE2b reference to Readme

Change-Id: Ifc7a0ecfc5c95147238ede97a605c156a12c97b1
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 done
 
 ```
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+## Sampling into Folds
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+The deterministic pseudo-random sampling into folds is based on the cryptographic hash algorithm BLAKE2b (Aumasson et al. 2014)
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 ## Scripts
 
 The package also contains some groovy scripts for handling *pseudonymization* tasks, i.e. replacing
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 # References
 
 * Koplenig, Alexander/Kupietz, Marc/Wolfer, Sascha (2022): [Testing the relationship between word length, frequency, and predictability based on the German Reference Corpus](http://dx.doi.org/10.1111/cogs.13090). Cognitive Science 46(6)
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+* Aumasson, Jean-Philippe/Meier, Willi/Phan, Raphael C-W/Henzen, Luca (2014): BLAKE2. In: The Hash Function BLAKE. Springer. p. 165–183.