1. J. M. Ryder and K. Dymock ,in Recycling of Metalliferrous Materials, IMM , London, U.K. , 1990 p. 255
2. G. B. Harris ,in Precious Metals 1993, IPMI , Allentown, Pa, U.S.A. , 1993 p. 351 – 374 (edited by Rajesh K. Mishra)
3. M. B. Mooiman ,in Precious Metals 1993, IPMI , Allentown, Pa, U.S.A. , 1993 , p. 411 – 434 , (edited by Rajesh K. Mishra)
4. V. H. Aprahamian , G. P. Demopouios and G. B. Harris ,in Precious Metals 1991, IPMI , Allentown, Pa, U.S.A. , 1991 , p. 143 – 434 , (edited by Larry Manziek)