\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{syntax}
\setlength{\grammarparsep}{2ex plus 0.1ex minus 0.05ex}
% \usepackage[T1]{fontenc}
\usepackage{bussproofs}
\usepackage{amsfonts}
\usepackage{subfiles}

\usepackage{hyperref}
\hypersetup{colorlinks = true, citecolor = blue}

\usepackage[backend=biber, hyperref=true, citestyle=authoryear]{biblatex}
\addbibresource{biblio.bib}

\title{pluto-spec}
\author{Platonic.Systems}
\date{February 2022}

\begin{document}
\maketitle{}

\nocite{*}
\subfile{introduction}
\subfile{syntax}
\subfile{semantics}
\subfile{appendix}
\printbibliography
\end{document}