Helper method to concatenate author and institution values, if necessary
        :return: string

def _author_line(self):
        """
        Helper method to concatenate author and institution values, if necessary
        :return: string
        """
        if self.author and self.institution:
            return self.author + ";" + self.institution
        elif self.author:
            return self.author
        else:
            return self.institution