@misc{indiciae2fd884b1a18f,
  title = {Certified reference materials and proficiency testing.},
  author = {R Krska and E Welzig},
  year = {2003},
  doi = {10.1007/s00216-003-1892-3},
  url = {https://pubmed.ncbi.nlm.nih.gov/12682704/},
  note = {Source identifier: 12682704}
}