@article{Stupakova_2020,
title={Development ot a black-earth soil reterence material,
tested tor fertility indicators},
volume={15},
ISSN={2077-1177},
url={http://dx.doi.org/10.20915/2077-1177-2019-15-4-33-40},
DOI={10.20915/2077-1177-2019-15-4-33-40},
number={4},
journal={Reference materials},
publisher={Ural Research Institute of Metrology (UNIIM)},
author={Stupakova,
G. A. and Ignatyeva,
E. E. and Shchipletsova,
T. I. and Mitrofanov,
D. K.},
year={2020},
month=jan,
pages={33–40} }