\documentclass[runningheads]{llncs}

\usepackage{graphicx}
\usepackage{pdfpages}
\usepackage{hyperref}
\usepackage{amssymb}
\usepackage{fancyhdr}
\usepackage{enumitem}
\usepackage{threeparttable}
\usepackage{multicol}

% Header & footer
\pagestyle{fancy}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt}
\fancyfoot[C]{\thepage}

\makeatletter
\renewenvironment{thebibliography}[1]
     {\begin{multicols}{2}[\section*{\refname}]%
      \@mkboth{\MakeUppercase\refname}{\MakeUppercase\refname}%
      \small
      \list{\@biblabel{\@arabic\c@enumiv}}%
          {\settowidth\labelwidth{\@biblabel{#1}}%
            \leftmargin\labelwidth
            \advance\leftmargin\labelsep
            \@openbib@code
            \usecounter{enumiv}%
            \let\p@enumiv\@empty
            \renewcommand\theenumiv{\@arabic\c@enumiv}}%
      \sloppy
      \clubpenalty4000
      \@clubpenalty \clubpenalty
      \widowpenalty4000%
      \sfcode`\.\@m}
     {\def\@noitemerr
      {\@latex@warning{Empty `thebibliography' environment}}%
      \endlist\end{multicols}}
\makeatother

% Make links blue
\renewcommand\UrlFont{\color{blue}\rmfamily}

% Structured abstract headings
\newcommand{\absdiv}[1]{
  \par
  \noindent\textbf{#1:}
}

% Research questions list
\newlist{rqlist}{enumerate}{1}
\setlist[rqlist, 1]{
  label=\textbf{RQ\arabic{rqlisti}.},
  leftmargin=2cm,
  rightmargin=1.25cm
}

\begin{document}

\includepdf[pages=-]{frontpage/frontpage.pdf}
\include{chapters/0_abstract}
\tableofcontents

\input{chapters/1_introduction}
\input{chapters/2_background}
\input{chapters/3_methods}
\input{chapters/4_design}
\input{chapters/5_case}
\input{chapters/6_survey}
\input{chapters/7_conclusion}

\clearpage
\bibliographystyle{splncs04}
\bibliography{ref}

\end{document}