documentclass[11pt, a4paper,usenames,dvipsnames]{article}
usepackage{ucs}
usepackage[utf8x]{inputenc}
usepackage[T1]{fontenc}
usepackage[greek,english]{babel}
usepackage{cite}
usepackage[verbose, colorlinks=true, naturalnames=true, linkcolor=blue,
unicode, bookmarks=true]{hyperref}
usepackage{caption}
usepackage{subcaption}
usepackage{bookmark}


begin{document}
selectlanguage{greek}

mytitle

 abstract here
newpage

tableofcontents

newpage

 a lot of text here with cites

 newpage

 cleardoublepage
 phantomsection
 addcontentsline{toc}{section}{Βιβλιογραφία}

 selectlanguage{english}

 bibliographystyle{ieeetr}
 bibliography{bibfile}

end{document}