[Tex/LaTex] Undefined control sequence. \end Biblatex

biberbiblatexbibtex

I am using Biblatex but when I compile the document, I recived the error

Undefined control sequence. \end
I updated all packages in MikTeX but nothing changed. I changed the settings from Biber to Bibtex but then it generates different errors and asks to use biber. I am using a bibtex file generated by mendley for referencing.

A minimal working example is given below: 

\documentclass[USenglish,12pt,a4paper]{article}
\usepackage{microtype}
\usepackage{graphicx}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{float}
\usepackage{url}\usepackage{microtype}
\usepackage{graphicx}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{float}
\usepackage{url}
\usepackage[backend=biber,style=apa,citestyle=authoryear,
 bibstyle=apa,natbib=true]
{biblatex}
\addbibresource{library.bib}

\begin{document}
\section{Introduction}
The section is introduced by \cite{BCBS2016}. This section provides the necessary details of introduction \citep{}.

\printbibliography
\end{document}

Two entries given in bib file are placed here: 

@techreport{BCBS2016,
 address = {Basel},
author = {BCBS},
booktitle = {Basel III Document},
institution = {Basel Committee on Banking Supervision},
isbn = {9291313734},
 number = {July},
publisher = {Bank for International Settlements},
title = {{Revision to the secuitisation framework}},
url = {http://www.bis.org/bcbs/publ/d374.pdf},
year = {2016}
}

@article{Chiesa2008,
author = {Chiesa, Gabriella},
doi = {10.1016/j.jfi.2008.07.003},
file = {:C$\backslash$:/Users/Ahmed Arif/AppData/Local/Mendeley Ltd./Mendeley Desktop/Downloaded/Chiesa - 2008 - Optimal credit risk transfer, monitored finance, and banks.pdf:pdf},
isbn = {1042-9573},
issn = {10429573},
journal = {Journal of Financial Intermediation},
keywords = {Credit risk transfer,Monitoring incentives,Prudential regulation},
number = {4},
pages = {464--477},
title = {{Optimal credit risk transfer, monitored finance, and banks}},
volume = {17},
year = {2008}
}

Best Answer

You're forgetting to load babel. And the language should be called american.

\begin{filecontents*}{\jobname.bib}
@techreport{BCBS2016,
  address = {Basel},
  author = {BCBS},
  booktitle = {Basel III Document},
  institution = {Basel Committee on Banking Supervision},
  isbn = {9291313734},
  number = {July},
  publisher = {Bank for International Settlements},
  title = {{Revision to the secuitisation framework}},
  url = {http://www.bis.org/bcbs/publ/d374.pdf},
  year = {2016}
}

@article{Chiesa2008,
  author = {Chiesa, Gabriella},
  doi = {10.1016/j.jfi.2008.07.003},
  file = {:C$\backslash$:/Users/Ahmed Arif/AppData/Local/Mendeley Ltd./Mendeley Desktop/Downloaded/Chiesa - 2008 - Optimal credit risk transfer, monitored finance, and banks.pdf:pdf},
  isbn = {1042-9573},
  issn = {10429573},
  journal = {Journal of Financial Intermediation},
  keywords = {Credit risk transfer,Monitoring incentives,Prudential regulation},
  number = {4},
  pages = {464--477},
  title = {{Optimal credit risk transfer, monitored finance, and banks}},
  volume = {17},
  year = {2008}
}
\end{filecontents*}

\documentclass[american,12pt,a4paper]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{amsmath}
\usepackage{microtype}
\usepackage{graphicx}
\usepackage{amsmath}
\usepackage{url}
\usepackage[
  backend=biber,
  style=apa,
  citestyle=authoryear,
  bibstyle=apa,
  natbib=true
]{biblatex}
\addbibresource{\jobname.bib}
\DeclareLanguageMapping{american}{american-apa}

\begin{document}
\section{Introduction}
The section is introduced by \cite{BCBS2016}. This section provides the 
necessary details of introduction \citep{Chiesa2008}.

\printbibliography
\end{document}

enter image description here

Notes

I used filecontents* just not to clobber my files and to make a self-contained example. Use your own library.bib file for your document.

I removed the packages you loaded twice and reorganized a bit the preamble.

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