documentclass{article}
usepackage[utf8]{inputenc}
usepackage[english]{babel}

usepackage[style=nejm, backend=biber]{biblatex}
addbibresource{sample.bib}

begin{document}
Let's cite! The Einstein's journal paper cite{einstein} and the Dirac's
book cite{dirac} are physics related items.

printbibliography

end{document}

@article{einstein,
    author =       "Albert Einstein",
    title =        "{Zur Elektrodynamik bewegter K{"o}rper}. ({German})
    [{On} the electrodynamics of moving bodies]",
    journal =      "Annalen der Physik",
    volume =       "322",
    number =       "10",
    pages =        "891--921",
    year =         "1905",
    DOI =          "http://dx.doi.org/10.1002/andp.19053221004",
    keywords =     "physics"
}

@book{dirac,
    title={The Principles of Quantum Mechanics},
    author={Paul Adrien Maurice Dirac},
    isbn={9780198520115},
    series={International series of monographs on physics},
    year={1981},
    publisher={Clarendon Press},
    keywords = {physics}
}