L.S. Fomenko, S.V. Lubenets, V.D. Natsik, D. Cassidy, G.E. Gadd, S. Moricca, and B. Sundqvist, Low temperature microhardness of Xe-intercalated fullerite C₆₀, Low Temp. Phys. 31, (2005) [Fiz. Nizk. Temp. 31, 596-601, (2005)] DOI: https://doi.org/10.1063/1.1925374.