It sounds like you're referring to a specific plugin for Calibre, a popular e-book management software. The KFX Input Plugin for Calibre is an additional tool that can be used to improve the conversion and handling of e-books within Calibre, particularly for formats like AZW3 (also known as KFX, which is used by Amazon for their e-books).
Itt...
...a nem-internetes spanyoltanulás eszközei (szótárak, teszt- és tankönyvek) találhatóak a kiadók weblapÂjairól.