Gurevich, A.; Terekhov, A.; Kondrashev, D.; Dolbin, A.; Cassidy, D.; Gadd, G.; Moricca, S.; Sundqvist, B. Low-Temperature Heat Capacity of Fullerite C₆₀ Doped With Nitrogen. Fiz. Nizk. Temp. 2006, 32, 1275-1277.