# How to link to the references in the definition?

I want to add a link to the definition to a research from where I have took the definition.

I have tried but it is not working.

\documentclass[parskip=full, 12pt]{article}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}{Corollary}[theorem]
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{mydef}{Definition}

\begin{document}
\section{Intro}
\begin{mydef}\label{[1]}
Let $G$ be a group, $H$ a subgroup of $G$; for $a,b \in G$ we say $a$ is congruent to $b$ mod $H$, written as $a \equiv b$ mod $H$ if $ab^{-1} \in H$.
\end{mydef}
\end{document}


Question : I want to $1$ to appear inside [] instead of $(1)$ and when I click on $1$ it should redirect me to the paper

i suspect that i is name of bib units in your bibliography (such naming is not good idea):

\documentclass[parskip=full, 12pt]{article}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}{Corollary}[theorem]
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{mydef}{Definition}

\usepackage{hyperref}

\begin{document}
\section{Intro}
\begin{mydef}\textup{\cite{1}}
Let $G$ be a group, $H$ a subgroup of $G$; for $a,b \in G$ we say $a$ is congruent to $b$ mod $H$, written as $a \equiv b$ mod $H$ if $ab^{-1} \in H$.
\end{mydef}
\end{document}


when you will add your bibliography this should work (instead of ? will appear 1 and click on it will move you to this bib unit). needed at least two compilations.