\documentclass[12pt,a4paper]{article}
%%% Reference: https://natur.cuni.cz/data/web/sekce/02_chemie/katedry/katedra_ucitelstvi_a_didaktiky_chemie/pokyny_zp_final-4.pdf
%packages
\usepackage{threeparttable}
\usepackage{booktabs}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{graphicx}
\usepackage{setspace}
\usepackage{titlesec}
\usepackage{chngcntr}
\usepackage{hyperref}
\usepackage{amsmath}
\usepackage{chemformula}
\usepackage{subcaption}
\usepackage{parskip}
\usepackage{booktabs}
\usepackage{caption}
\usepackage{csquotes}
\usepackage{array}
\usepackage{rotating}
\usepackage{makecell}
\usepackage{tablefootnote}
\usepackage{multirow}
\usepackage{lipsum}
%setup pdf
\setlength{\parskip}{10pt}
\setlength{\parindent}{15pt}
\usepackage[a4paper, left=3.5cm, right=2.5cm, top=2.5cm, bottom=2.5cm]{geometry}
\pagenumbering{arabic}
\captionsetup[table]{skip=10pt}
\hypersetup{hidelinks}
%bibliography
\usepackage[sort&compress,numbers,super]{natbib}
\bibliographystyle{achemso}
\emergencystretch=1em
% BEGIN DOCUMENT
\begin{document}
\setstretch{1.5} %line spacing
\include{1_titlepage}
\pagenumbering{arabic}
\
\include{2_formal}
\include{3_introduction}
\include{4_methods}
\include{5_results}
\setstretch{1}
\addcontentsline{toc}{section}{References}
\bibliography{references}
\end{document}
