bibtex error in LaTeX

Question

I am using bibtex with texshop on mac ox 10.4. I took the following four steps to add references in texshop.

1. Added package cite,
2. Kept the .bib file in the same folder as .tex file,
3. Added \bibliographystyle{plain},
4. Added \bibliography{ref} which is my imported references file from bibtex.

The sequence of compiling I followed is:

latex
bibtex
latex
latex

when I run latex the first time, a pdf file is created with reference heading at the end and ? at the position I cited.

When I run bibtex, the following message appears:

This is BibTeX, Version 0.99d (TeX Live 2012)
The top-level auxiliary file: test-survey-tpns.aux
The style file: plain.bst
White space in argument---line 5 of file test-survey-tpns.aux
 : \bibdata{ref
 :              for paper.bib}
I'm skipping whatever remains of this command
I found no database files---while reading file test.aux
Warning--I didn't find a database entry for "citekey"
(There were 2 error messages)

I can't figure out the problem, I am new to LaTeX and bibtex. It is the first time I am using it.

I am copying the .tex file content:

\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,latexsym,csquotes,cite}

% Page length commands go here in the preamble
\setlength{\oddsidemargin}{-0.25in} % Left margin of 1 in + 0 in = 1 in
\setlength{\textwidth}{7in}   % Right margin of 8.5 in - 1 in - 6.5 in = 1 in
\setlength{\topmargin}{-.75in}  % Top margin of 2 in -0.75 in = 1 in
\setlength{\textheight}{9.2in}  % Lower margin of 11 in - 9 in - 1 in = 1 in

\newtheorem{theorem}{Theorem}
\newtheorem{definition}{Definition}

\renewcommand{\baselinestretch}{1.5} % 1.5 denotes double spacing. Changing it will change the spacing

\setlength{\parindent}{0in} 
\begin{document}
\title{paper}
\author{authorr}
\date{\today}
\maketitle
\abstract{\emph{ajsjdjffjjfjfjfjfjjjfjf.} }

\section{Introduction}
  \quad   The innovation and developing technology every now and then is increasing the complexity of real-time control applications and reactive systems.  \\

However, the complexity of systems demands the notion of actions that can be suspended and resumed during their execution or control the progress of transitions. This requirement is fulfilled by several extensions .\\

The State Reachabilty for �Stopwatch Petri nets�\ unlike TPNs is proven undecidable even if the net is bounded \cite{magnin2006decidability}. \\


\subsection{Coined Terms}

background:
\subsection{\emph{Dense-time Semantics}:}
fdfdg\\

\subsection{\emph{Discrete-time Semantics}:}
dsfsff\\

\subsection{\emph{Timed Bisimilarity}:}
gfgfgg\\


\bibliographystyle{plain}
\bibliography{ref for survey.bib}

\end{document}

Here I am copying the .bib file content:

%% This BibTeX bibliography file was created using BibDesk.
%% http://bibdesk.sourceforge.net/


%% Created for Author at 2013-09-27 15:53:21 -0700 


%% Saved with string encoding Unicode (UTF-8) 



@incollection{roux2004time,
    Author = {Roux, Olivier H and Lime, Didier},
    Booktitle = {Applications and Theory of Petri Nets 2004},
    Date-Added = {2013-09-27 22:53:09 +0000},
    Date-Modified = {2013-09-27 22:53:09 +0000},
    Pages = {371--390},
    Publisher = {Springer},
    Title = {Time Petri nets with inhibitor hyperarcs. Formal semantics and state space computation},
    Year = {2004}}

@inproceedings{magnin2006decidability,
    Author = {Magnin, Morgan and Molinaro, Pierre and Roux, Olivier H},
    Booktitle = {Discrete Event Systems, 2006 8th International Workshop on},
    Date-Added = {2013-09-27 22:47:34 +0000},
    Date-Modified = {2013-09-27 22:47:34 +0000},
    Organization = {IEEE},
    Pages = {33--38},
    Title = {Decidability, expressivity and state-space computation of stopwatch Petri nets with discrete-time semantics},
    Year = {2006}}

@article{berthomieu2007reachability,
    Author = {Berthomieu, Bernard and Lime, Didier and Roux, Olivier H and Vernadat, Fran{\c{c}}ois},
    Date-Added = {2013-09-27 22:44:35 +0000},
    Date-Modified = {2013-09-27 22:44:35 +0000},
    Journal = {Discrete Event Dynamic Systems},
    Number = {2},
    Pages = {133--158},
    Publisher = {Springer},
    Title = {Reachability problems and abstract state spaces for time petri nets with stopwatches},
    Volume = {17},
    Year = {2007}}