\documentclass[a4paper]{article}
\usepackage[a4paper, total={20cm, 27cm}]{geometry}

\pagestyle{empty}

\usepackage[utf8]{inputenc}
\usepackage{hyperref}
\usepackage[
%backend=biber,
backend=bibtex,
style=reading,
sorting=ydnt,
defernumbers=true
]{biblatex}
\addbibresource{/GW/root/bibtex/golem}
\addbibresource{/GW/root/bibtex/castor}

\title{The GOLEM tokamak bibliography}
\author{The tokamak GOLEM team}
%\date{}

\defbibfilter{golemarticles}{
    type=article and
    keyword={exp.plasmaedge}
}

\defbibfilter{golemarticles}{
    type=article and
    keyword={exp.plasmaedge}
}


\begin{document}

\maketitle

\nocite{*}

\printbibliography[filter=golemarticles, title={GOLEM era articles}]

\printbibliography[filter=golemarticles, title={CASTOR era articles}]



%\printbibliography[type=inproceedings,title={Conference proceedings}]
%\printbibliography[keyword=mathesis,title={Master thesis}]
%\printbibliography[keyword=bachproj,title={Bachelor projects}]
%\printbibliography[keyword=soc,title={High School Students` Professional Activities}]
%\printbibliography[type=misc,keyword=in, title={Miscellaneous}]
%\printbibliography[type=article,keyword=out,title={Unofficial articles (without GOLEM cooperation/authors)}]

%\printbibliography[title={The tokamak GOLEM bibliography}]

\end{document}