A FREQUENCY DEPENDENT "LEVEL CROSSING" RESONANCE IN THULIUM NICOTINATE DIHYDRATE J. M. Baker, B. Bleaney, M. I. Cook, P. M. Martineau, M. R. Wells and C. A. Hutchison Jr. J. Phys. Colloques, 49 C8 (1988) C8-1515-C8-1516 DOI: 10.1051/jphyscol:19888698