This is My 1st try to produce an Article-Like document.
Here's the format I have followed, and the sample text worked perfectly!!
The bibliography tho, was added not in the way I liked it; I used to add bibliography like this;
@ARTICLE{2016MNRAS.457.1722R,
author = {{Rieder}, M. and {Teyssier}, R.},
title = "{A small-scale dynamo in feedback-dominated galaxies as the origin of cosmic magnetic fields - I. The kinematic phase}",
journal = {\mnras},
archivePrefix = "arXiv",
eprint = {1506.00849},
keywords = {MHD, turbulence, methods: numerical, galaxies: magnetic fields},
year = 2016,
month = apr,
volume = 457,
pages = {1722-1738},
doi = {10.1093/mnras/stv2985},
adsurl = {http://adsabs.harvard.edu/abs/2016MNRAS.457.1722R},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
To follow that, I went to my "Thesis" tex and copied what was there;
\usepackage[style=authoryear,sorting=none]{biblatex}
\addbibresource{references.bib}
and on the end of the .tex:
\printbibliography
and of course I copied references.bib on my folder.
Those two, results on the following Error:
! LaTeX Error: Command \bibhang already defined.
Or name \end... illegal, see p.192 of the manual.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help. ...
l.462 \newlength{\bibhang}
I tried to follow some other similar questions, but couldn't fine any commands like these;
\PassOptionsToPackage{square,numbers}{natbib}
\RequirePackage{natbib}
on any of my files.
EDIT: Here is part of my code:
\documentclass{aa}
\usepackage{graphicx}
\usepackage{txfonts}
\usepackage[style=authoryear,sorting=none]{biblatex}
\addbibresource{references.bib}
\begin{document}
\printbibliography
\end{document}

aa.clsloadsnatbibwhich defines\bibhang.biblatexalso defines\bibhang. You can't usenatbibandbiblatex. They are totally different ways of handling references. – David Purton Nov 15 '17 at 10:13ctrl+k– David Purton Nov 15 '17 at 10:17biblatex. Especially since their class mandatesnatbib. See Biblatex: submitting to a journal. And if you don't want to submit to their journal, why do you use their class in the first place? – moewe Nov 15 '17 at 10:54