Oliver Janseps is a fencer and martial artist and apparently an author of these topics. HEMA or historical fencing is his passion sice around 2006. In this context he wrotes transcriptions and translations and also designed training manuels. Some of them are published for a wider audience. These you can find here or (the german ones) on: https://www.epubli.de/shop/autor/Oliver-Janseps/30604).