4.
H. T. B. M. Petrus, Tsuyoshi Hirajima, Yuji Oosako, Moriyasu Nonaka, Keiko Sasaki, Takashi Ando, Performance of dry-separation processes in the recovery of cenospheres from fl y ash and their implementation in a recovery unit, Intern. J. of Mineral Processing, 98, 15–23 (2011).