What are these cinema sound formats?

[Reeves29]

Not sure if this is the right forum but, i noticed these when i was checking the time of LOTR at my local UCI cinema.

(DTS = Digital Theatre Sound) (DSR = Dolby Spectral Recording)
(DD = Dolby SRD) (DA = Dolby A)

Obiviously i know what DTS is, what are the others? Dolby digial, a kind of Pro-logic?

[kcxdev]

something about DSR at http://www.dolby.com/digital/diggenl.html

You might find the other 2 on the site as well
:)