Incorporating two styles of references

Question

In doing surveys and systematic literature reviews, we have References And Primary studies: the studies that are being analyzed and reviewed in the review. Both needed to be referenced in the document.

Is there a way to have two separate reference styles in the latex file that differentiate between a reference and a primary study? For example, we should have something similar to the following simple example:

In this review, we followed the procedures introduced in our earlier
work in [1] and [2] and extended by Heisenberg and Pinkman in [3] to analyse the
primary studies [PS1], [PS2], and [PS3].

References:
[1] Reference 1 
[2] Reference 2 
[3] Reference 3 

Primary studies:
[PS1] Primary Study 1
[PS2] Primary Study 2
[PS3] Primary Study 3 

---

Update: 01.02.2017

Based on the comments i tried the package splitbib. I tried the same exact code provided in the package documentation, but I got the following error:

! File ended while scanning use of \@bibitem.
<inserted text>
\par
<*> test.tex
I suspect you have forgotten a `}', causing me
to read past where you wanted me to stop.
I'll try to recover; but if the error is serious,
you'd better type `E' or `X' now and fix your file.

when i run the script:

\documentclass{article}
\usepackage{splitbib}
\begin{category}[A]{First category}
\SBentries{entry1,entry4}
\end{category}
\begin{category}[B]{Second category}
\begin{category}{First sub-category}
\SBentries{entry2,entry6}
\end{category}
\begin{category}{Second sub-category}
\SBentries{entry5,entry3}
\end{category}
\end{category}
\begin{document}
We cite~\cite{entry1,entry3,entry4,entry5}. Note that we cite neither
\verb+entry2+ nor \verb+entry6+,even though they have been assigned a category. defined in the last category. The first
sub-category will then not appear in the bibliography.
% \def\SBlongestlabel{A1}
\SBtitlestyle{bar}
\SBsubtitlestyle{none}
\begin{thebibliography}{1}
\bibitem{entry1} This is the first entry.
\bibitem{entry3} This is the third entry.
\bibitem{entry4} This is the fourth one.
\bibitem{entry5} This is the last one.
\end{thebibliography}
\end{document}