1. Anonymous personal communication. The amateur radio operators licensed in the strict Czechoslovak regime of the 1950–1980 were allowed to broadcast and received only on few certain fixed frequencies, allocated through government issued crystals. The crafty amateurs learned that by exposing the crystals to vapors of iodine, they could tune to other than the allocated frequencies. However, even having such knowledge was during that police era potentially dangerous.
2. DE 1051822 19590305 1959.
3. Adsorption of Gases on Quartz Single Crystals
4. A Vacuum System for Mass and Thermal Measurement with Resonating Crystalline Quartz