The old book "Christianismi restitutio", which Brandt (Evgeniy Vesnik) presented to Theodor (Filipp Kozlov) really exists. It's a theosophical work of Michael Servet was banned by Catholic Church after its publication in 1553. The author of the book was proclaimed a heretic and burnt at the stake the very same year.
The name of town of Eseldorf in Filipp Traum (1990) translates as a village of donkey-people (Esel literally means "donkey" in German, and "dorf" means village).