TY  - RPRT
TI  - Certified reference materials and proficiency testing.
AU  - R Krska
AU  - E Welzig
PY  - 2003
DO  - 10.1007/s00216-003-1892-3
UR  - https://pubmed.ncbi.nlm.nih.gov/12682704/
ID  - 12682704
ER  -