Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period.
The Wayback Machine - https://web.archive.org/web/20100818174908/http://hea-www.harvard.edu:80/~fine/ISDN/
ISDN
Described here are the basics of ISDN, including much practical
information for the consumer, as well as some fairly technical descriptions
of ISDN, and finally some discussion on where ISDN is going in the future.