def sentences(self, index = None):
        """Return a generator of all sentence found in the document. Except for sentences in quotes.

        If an index is specified, return the n'th sentence only (starting at 0)"""
        if index is None:
            return self.select(Sentence,None,True,[Quote])
        else:
            if index < 0:
                index = sum(t.count(Sentence,None,True,[Quote]) for t in self.data) + index
            for t in self.data:
                for i,e in enumerate(t.select(Sentence,None,True,[Quote])) :
                    if i == index:
                        return e
            raise IndexError
Return a generator of all sentence found in the document. Except for sentences in quotes.

        If an index is specified, return the n'th sentence only (starting at 0)