14C in uranium and thorium minerals: a signature of cluster radioactivity? R. Bonetti, A. Guglielmetti, G. Poli, E. Sacchi, D. Fink, M.A.C. Hotchkis, G.E. Jacobsen, E.M. Lawson, Q. Hua, A.M. Smith and C. Tuniz Eur. Phys. J. A, 5 2 (1999) 235-238 Published online: 15 June 1999 DOI: 10.1007/s100500050279