1. Nichols and HowesFluorescence of Uranyl Salts, Carnegie Institute Publications, No. 298, 1919.
2. Dieke and Van HeelLeiden Communications, 1925, Suppl. No. 55 A.
3. Van HeelIbid., Leiden Communications, 1925, Suppl. No. 55 B.
4. Van HeelIbid., Leiden Communications, 1925, Suppl. No. 187 A.
5. Conn and WuTrans. Farad. Soc., 1938,34, 1483.