METHOD OF FLOTATION OF DIFFICULTLY DRESSED COALS WITH HIGH-CONTENT OF ASH - KASIMOVA NINA N,SU; KOZLOV VALERIJ M,SU; FILYAKIN MIKHAIL P,SU; EGOROV VYACHESLAV N,SU; KONDRASHOV EVGENIJ F,SU; SUSLOV VITALIJ I,SU; SAVINCHUK LYUDMILA G,SU (1990)