Akbari, A., Eremin, I., Thalmeier, P., & Fulde, P. (2009). Theory of the bound state of 4ƒ excitations and magnetic resonance in unconventional superconductors. Physical Review B, 80: 100504, pp. 100504-1-100504-4. doi:10.1103/PhysRevB.80.100504.