Verify the integrity of Debian CDs

[alrenaud@swissinfo.org]

I buyed 14 CD?s of Sarge,which is regenerated weekly.
I want to verify the md5 of each .iso file,but I face
two problems:

1)The CD?s were recorded in the second half of April,
  the md5 file for the .iso files is for this week
  snapshot.How can I find the md5 files for the last
  month snapshots?

2)Can I generate .iso files for each CD with mkisofs?
  So that I can calculate the md5 and compare with
  the published md5 file.
  Or this approach is not effective to verify the
  integrity of the CD?s?


                     Thanks.

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