% This file is embedded in glossaries-extra-manual.pdf 
% Example 163 Using bib2gls: dual backlinks
% Label: "ex:bib2glsdualbacklinks"
% arara: pdflatex
% arara: bib2gls
% arara: pdflatex
% arara: pdfcrop
\documentclass[12pt]{article}
\pagestyle{empty}
\begin{filecontents*}{\jobname.bib}
@dualindexsymbol{L,
 name={Lagrangian function},
 symbol={\ensuremath{L}},
 description={a function of generalized co-ordinates}
}
\end{filecontents*}
\usepackage[colorlinks]{hyperref}
\usepackage[record,symbols,nostyles,stylemods={tree,bookindex}]{glossaries-extra}
\GlsXtrLoadResources[src={\jobname},
 dual-type=symbols,dual-field
]
\glsdefpostlink{index}{\glsxtrpostlinkAddSymbolOnFirstUse}
\glsdefpostname{index}{%
 \ifglshassymbol{\glscurrententrylabel}
 { (\GlsXtrDualBackLink{\glsentrysymbol{\glscurrententrylabel}}{\glscurrententrylabel})}{}} 
\begin{document}
Primary: \gls{L}.
\printunsrtglossary[type=symbols,style=tree]
\printunsrtglossary[title=Index,style=bookindex] 
\end{document}
