An explanation of how narrow gauge trains get their number designations.
https://pl.wikipedia.org/wiki/Oznaczenia_taboru_w%C4%85skotorowego_PKP
https://pl.wikipedia.org/wiki/Oznaczenia_polskich_parowoz%C3%B3w_i_tendr%C3%B3w
A Comprenshive Modeler's And Model Railroader's Guide
