Natbib citation styles

Natbib uses the citation style associated with the corresponding bibliography style if no specific citation commands are declared. There are some additional commands to control some punctuation parameters. See the example below:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

%Import the natbib package and sets a bibliography  and citation styles
\usepackage{natbib}
\bibliographystyle{abbrvnat}
\setcitestyle{authoryear,open={((},close={))}}


\begin{document}

\section{First Section}
This document is an example, two items are cited: \textit{The \LaTeX\ Companion} book \cite[see][chap 2]{latexcompanion} and Einstein's journal paper \cite{einstein}. 


%Imports the bibliography file "sample.bib"
\bibliography{sample}

\end{document}

The specific command to format the citation style is:

\setcitestyle{authoryear, open={((},close={))}

The parameters, comma-separated, tell LaTeX to use the authoryear citation mode and use double parentheses as opening and closing marks. The various parameters that can be passed to this command are the following:

• Citation mode: authoryear, numbers or super.
• Brackets: round or square. You can manually set any other opening and closing characters with open={char} adn close={char}.
• Citation separator: semicolon, comma.
• Separator between author and year: aysep{char}.
• Separator between years with common author: yysep={char}.
• Text before post-note: notesep={text}.