Fizika mineralov i Rudnaa mikroskopia= Physics of minerals and ore microscopy : materiali XIII Kongressa Mekdunarodnoj Mineralogiceskoj Associacii MMA, Varna, 19-25 Sentabra 1982: proceedings of the 13th General Meeting on the International Mineralogical Association IMA, Varna, September 19th-25th 1982 ([s.n.], 1986)