If you live in Europe you can enquire via email at Agrumi-Voss, he lists it in his catalogue online (thanks to IlyaC for the link):
http://www.agrumi-voss.de/agrfrost.htm
It is number M10, 5 down in the table. I used google translate and copied the table entry below:
M10 ponc.trif.x reticulata "Changsha" Citrandarin Min Temp. -15C Fruit such as mandarin, sour, bitter, polyembry. Unfortunately, late-maturing