Only one frame of references in beamer

Question

The references appear only in one frame in beamer, meaning that the list of references is incomplete.

How can I create the necessary number of frames?

Here is the .tex exported from LyX:

%% LyX 2.3.0 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
\documentclass[english]{beamer}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\setcounter{secnumdepth}{3}
\setcounter{tocdepth}{1}
\usepackage[authoryear]{natbib}

\makeatletter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands.
% this default might be overridden by plain title style
\newcommand\makebeamertitle{\frame{\maketitle}}%
% (ERT) argument for the TOC
\AtBeginDocument{%
  \let\origtableofcontents=\tableofcontents
  \def\tableofcontents{\@ifnextchar[{\origtableofcontents}{\gobbletableofcontents}}
  \def\gobbletableofcontents#1{\origtableofcontents}
}
% plain title style, override default
\renewcommand\makebeamertitle{\frame[plain]{\maketitle}}%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% User specified LaTeX commands.
\usepackage{url}
%\usepackage{hyperref}
\usepackage{tabularx}
%\usepackage[super,sort&compress]{natbib}
\usetheme{Warsaw}
% for beamer version >= 3.5 only
%\setbeamertemplate{page number in head/foot}[totalframenumber]
\usepackage{dsfont}
%\usepackage[table]{xcolor}
%\usepackage{dcolumn}
\addtobeamertemplate{footline}{\insertframenumber/\inserttotalframenumber}
\renewcommand{\bibsection}{}

\makeatother

\usepackage{babel}
\begin{document}

\title{Template beamer}
\makebeamertitle
\begin{frame}{}

\citet{king_matrix_2014,king_comparing_2015-1,khindanova_location_2011,kishita_estimation_2012,koskinen_energy_2016,kok_measuring_2006,krausmann_growth_2009,le_boulzec_impacts_nodate,lambert_eroi_2012}
\end{frame}
%
\begin{frame}{}

\bibliographystyle{plainnatnourl_clean}
\bibliography{\string"C:/Users/a.fabre/Google Drive/Economie/Articles/Environment\string",\string"C:/Users/a.fabre/Google Drive/Economie/Articles/test\string"}
\end{frame}

\end{document}