array(3) {
  [0]=>
  int(17421)
  [1]=>
  string(198) "Ren H., Zhao Y., Xiao W., Hu Z. A review of UAV monitoring in mining areas: Current status and future perspectives // International journal of coal science & technology. 2019. vol. 6. pp. 320–333."
  [2]=>
  int(19)
}
<h1>DB Error 230: Duplicate entry '17421-19' for key 'citations.citations_submission_seq'</h1>