Z.-L. Li, N. Bonifaci, A. Denat, V.M. Atrazhev, V.A. Shakhatov, and K. von Haeften, Atomic and molecular spectra emitted by normal liquid ⁴He excited by corona discharge, Low Temp. Phys. 37, (2011) [Fiz. Nizk. Temp. 37, 484-490, (2011)] DOI: https://doi.org/10.1063/1.3599651.