[['series sorted', 'title', 'doctor', 'featuring', 'released'], ['6eb / a', 'the elite', '5th', 'tegan , nyssa , dalek', 'october 2011'], ['6eb / b', 'hexagora', '5th', 'tegan , nyssa', 'november 2011'], ['6eb / c', 'the children of seth', '5th', 'tegan , nyssa', 'december 2011'], ['6y / ai', 'the guardians of prophecy', '6th', 'peri', 'may 2012'], ['6y / aj', 'power play', '6th', 'peri , victoria', 'june 2012'], ['6y / ak', 'the first sontarans', '6th', 'peri , sontarans , rutans', 'july 2012'], ['h / c', 'the masters of luxor', '1st', 'susan foreman , ian chesterton , barbara wright', 'august 2012'], ['xx / a', 'the rosemariners', '2nd', 'jamie mccrimmon , zoe heriot', 'september 2012']]
the release date were in average 1 per month
the release date were in average 1 per month