To add support for both ISBN-10 and ISBN-13 in the bib entries, I borrowed the code-snippet from here, but used bibtex as the backend. But, that does not seem to work, while it works fine with biber backend. Is there anything I can do to make it work with bibtex? MWE is provided below.
\documentclass{article}
\usepackage{filecontents}
\usepackage[backend=bibtex,datamodel=biblatex-dm,isbn=true]{biblatex}
\begin{filecontents}{\jobname.bib}
@book{drucker1959landmarks,
title={Landmarks of Tomorrow: A Report on the New},
author={Drucker, Peter},
publisher={Transaction Publishers},
year={1996},
isbn={1560006226},
ISBN10={1560006226},
ISBN13={978-1560006220},
note={[original edition 1959]}
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{filecontents}{biblatex-dm.cfg}
\DeclareDatamodelFields[type=field,datatype=literal]{isbn10,isbn13}
\DeclareDatamodelEntryfields[book]{isbn10,isbn13}
\end{filecontents}
\DeclareFieldFormat{isbn}{\textsc{isbn-13}~\printfield{isbn13}, \textsc{isbn-10}~\printfield{isbn10}}
\title{title}
\author{A.U. Thor}
\begin{document}
\nocite{*}
\printbibliography
\end{document}