| Brunswick House Press ; p | , 1980, Gems Made By Man, Gemological Institute of America,• 2001 Secrets of the Gem Trade: the connoisseur's guide to precious gemstones |
|---|---|
| Elwell-Center for materials Research Stanford University-first published in 1979 by Ellis Horwood Limited England- p 158• | , edited by William Crooke; Vol |
Karl Schmetzer, Dietmar Schwartz, Heinz-Jurgen Bernhardt, Tobias Hager Journal of Gemmology of Gemmological Association of Great Britain, September, Vol.
26.
9.