def childIds(self):
        """ Children of the passage

        :rtype: None, CtsReference
        :returns: Dictionary of chidren, where key are subreferences
        """
        if self.depth >= len(self.citation.root):
            return []
        elif self._children is not None:
            return self._children
        else:
            self._children = self.getReffs()
            return self._children