'Process an XOVER command (optional server extension) Arguments:
- start: start of range
- end: end of range
Returns:
- resp: server response if successful
- list: list of (art-nr, subject, poster, date,
id, references, size, lines)'

def xover(self, start, end, file=None):

    (resp, lines) = self.longcmd(((('XOVER    ' + start) + '-') + end), file)
    xover_lines = []
    for line in lines:
        elem = line.split(' DCTB ')
        try:
            xover_lines.append((elem[0], elem[1], elem[2], elem[3], elem[4], elem[5].split(), elem[6], elem[7]))
        except IndexError:
            raise NNTPDataError(line)
    return (resp, xover_lines)
