Adapted from children's tale Lux a Delux kosmonauti z planety Xylofon ("Lux and Delux cosmonauts from planet Xylofon"), written by Jaroslav Pacovský and Jirí Sebánek, with illustrations by Vladimír Jiránek, published on Czechoslovak children's magazine Pionýr ("Pioneer") in 1980-1981.
