Peter Watson, Ideas: A History of Thought and Invention, from Fire to Freud, illustrated, annotated, HarperCollins, 2006, p. 304, ISBN 0-06-093564-2. URL consultato il 28 novembre 2011.
«The first use of a metal tube in this context was made around 1280 in the wars between the Song and the Mongols, where a new term, chong, was invented to describe the new horror...Like paper, it reached the West via the Muslims, in this case the writings of the Andalusian botanist Ibn al-Baytar, who died in Damascus in 1248. The Arabic term for saltpetre is 'Chinese snow' while the Persian usage is 'Chinese salt'.28»
