I recently enrolled in 3 classes,07-2011, distribution 2 and treatment 2 on cd, dist cd was scratched and both cd's had audio files missing that were supposed to be included and was later told basicly too bad. The 3rd course the online wastewater 2 review had the same issues. It was too bad because the rest of the info and layout was very useful, comprehensive and easy to go thru. 2.5 stars for the missing audio mp3 files.