1. Weeks ME (1968) The discovery of the elements, J. Chem. Educ. Publ., Easton PA
2. Trimble V (1975) Rev. Mod. Phys. 47: 877
3. Jørgensen CK (1988) In: Gschneidner KA, Eyring L (eds) Handbook on the physics and chemistry of rare earths vol 11, North-Holland, Amsterdam, pp. 197–292
4. Jørgensen CK (this volume)
5. Jørgensen CK, Kauffman GB (this volume)