documentclass[twoside,floatfix,11pt]{article}
usepackage[english]{babel}
usepackage{fontenc}
usepackage[utf8]{inputenc}
usepackage{graphicx}
usepackage{graphics}
usepackage{geometry}
geometry{marginparwidth=0.01cm,verbose,a4paper,top=25mm,bottom=25mm,left=30mm,right=20mm}
usepackage{setspace}
usepackage{lmodern}
usepackage{amssymb}
usepackage{amsmath, amsthm}
usepackage{amsmath,amscd}
usepackage{hyperref}
usepackage[all,cmtip]{xy}
usepackage{verbatim}
usepackage{indentfirst}
usepackage{listings}
usepackage{multirow}
usepackage{tabu}
usepackage{subcaption}
usepackage{footmisc}
usepackage{accents}
usepackage{comment}
usepackage[outercaption]{sidecap}
captionsetup{compatibility=false}
def dif {mathrm{d}}
defbeq{begin{equation}}
defeeq{end{equation}}
defbeqa{begin{eqnarray}}
defeeqa{end{eqnarray}}

usepackage{fancyhdr}
pagestyle{fancy}
fancyhf{} % sets both header and footer to nothing
renewcommand{headrulewidth}{0pt}
fancyhead[LE,RO]{textit{Epsilon}}
fancyhead[LO,RE]{textit{thepage}}

linespread{1.3}

usepackage{etoolbox}
patchcmd{section}
  {centering}
  {raggedright}
  {}
  {}
patchcmd{subsection}
  {centering}
  {raggedright}
  {}
  {}

usepackage{titlesec}
titleformat{section}
  {titlerule%
  normalfontbfseriesLarge}
  {thesection}{1em}{}[titlerule]

 titleformat{subsection}
  {normalfontbfseries}
  {thesubsection}{1em}{}[titlerule]


makeindex
begin{document}

begin{thebibliography}

bibitem{Alpha} Alpha, Betha, Gamma (2019) State of the art of Delta

end{thebibliography}

end{document}