[Tex/LaTex] Double citation problem with apacite and BibTeX

Question

When I attempt to insert an APA citation like so:

\cite[5.]{law1966money}

With the BibTeX entry looking like this:

@book{law1966money,
title={Money and trade considered},
author={Law, John},
year={1966},
publisher={AM Kelley}
}

It inserts a double citation into the document:

I'm using BibTeX and the apacite package in TeXStudio, after the Compile->Bibliography->Compile->Compile chain of events to get all the references loaded, and my code looks like this (my bibliography is in references.bib in the same folder):

\documentclass[12pt]{article}
%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{setspace} % Double-space
\usepackage{csquotes} % Block quotes
\usepackage{apacite} % APA citation style

\bibliographystyle{apa}
\doublespacing
%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}
\maketitle

% Document stuff...
Test cite \cite[5.]{law1966money}

\bibliography{references}
\end{document}

Answer 1

The package apacite requires the bibstyle apacite rather than apa. Change the line

  \bibliographystyle{apa}

to

  \bibliographystyle{apacite}

and the result will be Test cite (Law, 1966, 5.), as it should be