Jentschura, Ulrich David Division Prof. Dr. Christoph H. Keitel, MPI for Nuclear Physics, Max Planck Society;
http://link.aps.org/doi/10.1103/PhysRevA.74.062517 (Publisher version)
Jentschura, U. D. (2006). Two-loop Bethe logarithms for non-S levels. Physical Review A, 74(6): 062517, pp. 1-13. doi:10.1103/PhysRevA.74.062517.