Mapping of Trace Elements in Coal and Ash Research Based on a Bibliometric Analysis Method Spanning 1971–2017 Yang, Liu ; Wang, Qiqi ; Bai, Xue ; Deng, Jun ; Hu, Yinjie Abstract Publication: Minerals Pub Date: February 2018 DOI: 10.3390/min8030089 Bibcode: 2018Mine....8...89Y