Historical Data Structure and Laboratory Performance in the North American Proficiency Testing (NAPT) Program.
Grant E. Cardon, Utah State University, Logan, UT, Bryan G. Hopkins, 701 E. University Parkway, Brigham Young University, Provo, UT, US, John R. Lawley, Plants, Soils, and Climate, Utah State University, Logan, UT and Tony L. Provin, Soil and Crop Sciences, Texas A&M AgriLife Extension, College Station, TX, US