MÖSSBAUER EFFECT STUDY OF THE RELATION BETWEEN RIVER CONCRETIONS AND MANGANEZE NODULES N. A. EISSA, H. A. SALLAM, H. A. EL-KERDANI et F. M. TAIEL J. Phys. Colloques, 37 C6 (1976) C6-857-C6-860 DOI: 10.1051/jphyscol:19766180