*[http://www.crystalimpact.com/match/Default.htm Match!] (method: powder diffraction fingerprinting)
*[https://web.archive.org/web/20080616153210/http://www.nist.gov/srd/nist3.htm NIST Crystal Data] (method: lattice matching)
*[http://www.icdd.com/ Powder Diffraction File (PDF)] (method: powder diffraction fingerprinting)