(1) The thulium material never recovers from the upwards resistive change, and continues recovery to the normal state as the compound is further cooled.

(2) The American chemist C. James performed 15,000 recrystallizations before pure thulium bromate was obtained.

(3) Each segment contains small amounts of ions of relatively rare metals, such as dysprosium, thulium , and cerium, which fluoresce in different colors.

(4) The main rare-earth ions used are thulium (for devices operating at 1450 to 1510 nm) and erbium.

(5) The pure metal can be produced by treating thulium fluoride with calcium metal.