Handbook of Mineralogy http://rruff.geo.arizona.edu/doclib/hom/langbeinite.pdf
Handbook of Mineralogy http://rruff.geo.arizona.edu/doclib/hom/langbeinite.pdf
Handbook of Mineralogy http://rruff.geo.arizona.edu/doclib/hom/langbeinite.pdf
Mindat with location data http://www.mindat.org/min-2320.html