'Return the contents of citation.bib file (for omw)
use lang=lang to get the citation for an individual language'

def citation(self, lang=u'omw'):

    if (lang == u'eng'):
        return self.open(u'citation.bib').read()
    elif (lang in self.langs()):
        return self._omw_reader.open(u'{}/citation.bib'.format(lang)).read()
    elif (lang == u'omw'):
        return self._omw_reader.open(u'citation.bib').read()
    elif (lang in self._lang_data):
        raise WordNetError(u'citation    not    known    for    user-provided    tab    file')
    else:
        raise WordNetError(u'Language    is    not    supported.')
