5Werner M, Friedrich S. New possibilities in disposal of residual material by the technique of fill-up goaf cavities in coal mining[A]. Raj K Singhal, Anil KMehrotra, Kostas Fytas et al. Environmental issues and management of waste in energy and mineral production[C]. Rotterdam:A A. Balkema, 1992:379-388.
6Werner M, Friedrich S. New possibilities in disposal of residual material by the technique of fill--up goaf cavities in coal mining[A]. Raj K Singhal, Anil KMehrotra, Kostas Fytas, et al. Environmental issues and management of waste in energy and mineral production[C]. Rotterdam:A. A. Balkema, 1992.379-388.
