[davidoff86]

To update the SDP, you need all the deltas.

so, from say 4.37.4 to 4.39.1, you need:
4.37.4 (just the xml)
4.38.1
4.38.2
4.38.3
4.38.4
4.39.1

However, 4.38.1 came with a FULL, so you can use that and ignore any deltas lower