pdf_file = models.FileField(_('PDF file'), upload_to=book_upload_path('pdf'), blank=True)
odt_file = models.FileField(_('ODT file'), upload_to=book_upload_path('odt'), blank=True)
txt_file = models.FileField(_('TXT file'), upload_to=book_upload_path('txt'), blank=True)
pdf_file = models.FileField(_('PDF file'), upload_to=book_upload_path('pdf'), blank=True)
odt_file = models.FileField(_('ODT file'), upload_to=book_upload_path('odt'), blank=True)
txt_file = models.FileField(_('TXT file'), upload_to=book_upload_path('txt'), blank=True)