1. WHO Media Centre fact sheet no. 282 (October 2013). http://www.who.int/mediacentre/factsheets/fs282/en/
2. Digman, M., Elder, C.: Mobile Banknote Recognition and Conversion. https://stacks.stanford.edu/file/druid:yt916dh6570/Elder_Digman_Foreign_Bill_Recognition.pdf
3. Bruna, A., Farinella, G.M., Guarnera, G.C., Battiato, S.: Forgery Detection and Value Identification of Euro Banknotes. Sensor (Basel) 13(2), 2515–2529 (2013). doi:10.3390/s1302022515. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3649387/ (February 18, 2013)
4. Lowe, D.: Distinctive Image Features from Scale-Invariant Keypoints. International Journal of Computer Vision (2004). http://www.cs.ubc.ca/~lowe/papers/ijcv04.pdf
5. Bay, H., Ess, A., Tuytelaars, T., Gool, L.V.: Speeded-Up Robust Features (SURF). ftp://vision.ee.ethz.ch/publications/articles/eth_biwi_00517.pdf