title: Certified reference materials and proficiency testing.
authors.affiliation: Institute for Agrobiotechnology (IFA-Tulln), Center for Analytical Chemistry, Konrad-Lorenz-Strasse 20, Austria. krska@ifa-tulln.ac.at
authors.forename: R
authors.initials: R
authors.lastname: Krska
authors.forename: E
authors.initials: E
authors.lastname: Welzig