With the latest season of 'Doctor Who' ending, you'll have the rest of the summer to catch up on your 'Who' history. If you're a purist, the best way to do that is to go back to the vaults and watch the show.

BBC America just released four more volumes, covering the First Doctor (William Hartnell, 1963-1966), the Third Doctor (Jon Pertwee, 1970-1974), and the Fourth Doctor (Tom Baker, 1974-1981).

More than two thirds of the episodes are available on DVD, and the BBC plans to eventually release everything it has. Mind you, some of the earliest episodes from the '60s and '70s were erased to make way for newer programs, but bits of those turn up here and there.

Doctor Who went from regular production to sporadic specials last year to freshen up the show and to give former lead David Tennant a shot at playing Hamlet for the Royal Shakespeare Company. The end results of that year of specials are headed your way on DVD in a five disc set.

Doctor Who: The Complete Specials features what proved to be a mixed bag of special episodes that became a sort of de facto fifth mini-season for Tennant. While you're not going to find a bad piece of television anywhere on this disc (or anywhere in Doctor Who's 21st century rebirth), last year's programs got weaker as they marched toward Tennant's regeneration.

The line-up includes The Next Doctor, Planet of the Dead, The Waters of Mars and The End of Time, Parts One and Two. The first two stand alone, but the last three create a sort of trilogy documenting the 10th Doctor's final days.

'Doctor Who: End of Time' Part 1 (Sat., 9PM, BBCA)
The aptly titled 'End of Time' really does spell the beginning of the end for current Doctor Who David Tennant, who's leaving his role as the tenth Doctor with 'End of Time,' part 2. The youngest Who ever -- 26-year-old Matt Smith -- takes over in 2010 for the show's fifth season, but for now, it's still all about Tennant's good Doctor, who faces the end of his life when The Master is reborn. And, word of advice, 'Who' fans: Tennant says he cried when he read the 'End of Time' script, so make sure you've got a hankie standing by in your own little TARDIS.